                             In the

      United States Court of
             Appeals
              For the Seventh Circuit

No. 10-3891

STATE OF M ICHIGAN, et al.,
                                         Plaintiffs-Appellants,

and

G RAND T RAVERSE B AND OF O TTAWA
AND C HIPPEWA INDIANS,
                                         Intervenor-Appellant,

                               v.


U NITED STATES A RMY C ORPS OF
E NGINEERS, et al.,
                                        Defendants-Appellees,

and

C ITY OF C HICAGO, et al.,
                                        Intervenors-Appellees.

       Appeal from the United States District Court
   for the Northern District of Illinois, Eastern Division.
         No. 10 C 4457—Robert M. Dow, Jr., Judge.
2                                                 No. 10-3891


      A RGUED M AY 5, 2011 — D ECIDED A UGUST 24, 2011*

    Before M ANION, W OOD, and W ILLIAMS, Circuit Judges.
   W OOD, Circuit Judge. Ambitious engineering projects that
began at the time that the City of Chicago was founded have
established a waterway in northeastern Illinois that connects
Lake Michigan to the Mississippi watershed. (Additional
links between the Mississippi and the Great Lakes exist
elsewhere, from northern Minnesota to New York.) The
system of canals, channels, locks, and dams, with which we
are concerned, known today as the Chicago Area Waterway
System (or CAWS, as the parties call it in their briefs), winds
from the mouth of the Chicago River and four other points
on Lake Michigan to tributaries of the Mississippi River in
Illinois. The navigable link has been a boon to industry and
commerce, and it supports transportation and recreation.
Public health crises that once were common because the
Chicago River emptied the City’s sewage into the lake – the
City’s freshwater supply – vanished thanks to the Chicago
Sanitary and Ship Canal, which reversed the flow of the
Chicago River so that it now pulls water from the lake, into
the CAWS, and down toward the Mississippi. During heavy
rains and seasonal high waters in the region, the CAWS is
used to control flooding.
  This effort to connect the Great Lakes and Mississippi
watersheds has not been without controversy. At the turn of
the 20th century, Missouri sued in the Supreme Court to
stop Illinois from opening the Sanitary and Ship Canal. An
opinion by Justice Holmes rejected Missouri’s challenge; the
Court concluded that the state had not presented enough
evidence to establish that the flow of sewage toward the



         *
        This opinion is released in typescript; a printed
version will follow.
No. 10-3891                                                     3

Mississippi would create a public nuisance. Missouri v.
Illinois, 200 U.S. 496 (1906); see also Missouri v. Illinois, 180
U.S. 208 (1901). Several years later a broader fight erupted
among the states bordering the Great Lakes, and the Court
began to issue decrees setting the maximum rate at which
Illinois may divert water away from Lake Michigan and into
the CAWS. E.g., Wisconsin v. Illinois, 449 U.S. 48 (1980);
Wisconsin v. Illinois, 388 U.S. 426 (1967); Wisconsin v. Illinois,
311 U.S. 107 (1940); Wisconsin v. Illinois, 278 U.S. 367 (1929).
Nor has opening a pathway between these bodies of fresh
water come without costs. This appeal requires us to
consider one of those costs: the environmental and economic
harm posed by two invasive species of carp, commonly
known as Asian carp, which have migrated up the
Mississippi River and now are poised at the brink of this
man-made path to the Great Lakes. The carp are voracious
eaters that consume small organisms on which the entire
food chain relies; they crowd out native species as they enter
new environments; they reproduce at a high rate; they travel
quickly and adapt readily; and they have a dangerous habit
of jumping out of the water and harming people and
property.
  In an attempt to stop the fish, Michigan, Minnesota, Ohio,
Pennsylvania, and Wisconsin, all states bordering the Great
Lakes, filed this lawsuit against the U.S. Army Corps of
Engineers (the Corps) and the Metropolitan Water
Reclamation District of Greater Chicago (the District), which
together own and operate the facilities that make up the
CAWS. The plaintiff states allege that the Corps and the
District are managing the CAWS in a manner that will allow
invasive carp to move for the first time into the Great Lakes.
The states fear that if the fish establish a sustainable
population there, ecological disaster and the collapse of
billion-dollar industries that depend on the existing
ecosystem will follow. They say that the defendants’ failure
to close down parts of the CAWS to avert the crisis creates
a grave risk of harm, in violation of the federal common law
of public nuisance, see American Electric Power Co., Inc. v.
4                                                  No. 10-3891

Connecticut, 131 S. Ct. 2527 (2011), and they advance a
related claim against the Corps based on the Administrative
Procedure Act (APA), 5 U.S.C. § 702. The states asked the
district court for declaratory and injunctive relief and moved
for a preliminary injunction that would require the
defendants to put in place additional physical barriers
throughout the CAWS, implement new procedures to stop
invasive carp, and expedite a study of how best to separate
the Mississippi and Great Lakes watersheds permanently.
Other parties intervened to protect their interests – the
Grand Traverse Band of Ottawa and Chippewa Indians on
the side of the plaintiffs, and the City of Chicago, Wendella
Sightseeing Company, and the Coalition to Save Our
Waterways as defendants. The district court denied the
motion for a preliminary injunction, and the states appealed
immediately. See 28 U.S.C. § 1292(a)(1).
  We conclude that the court’s decision to deny preliminary
relief was not an abuse of discretion. Our analysis, however,
differs in significant respects from that of the district court,
which was persuaded that the plaintiffs had shown only a
minimal chance of succeeding on their claims. We are less
sanguine about the prospects of keeping the carp at bay. In
our view, the plaintiffs presented enough evidence at this
preliminary stage of the case to establish a good or perhaps
even a substantial likelihood of harm – that is, a non-trivial
chance that the carp will invade Lake Michigan in numbers
great enough to constitute a public nuisance. If the invasion
comes to pass, there is little doubt that the harm to the
plaintiff states would be irreparable. That does not mean,
however, that they are automatically entitled to injunctive
relief. The defendants, in collaboration with a great number
of agencies and experts from the state and federal
governments, have mounted a full-scale effort to stop the
carp from reaching the Great Lakes, and this group has
promised that additional steps will be taken in the near
future. This effort diminishes any role that equitable relief
would otherwise play. Although this case does not involve
the same kind of formal legal regime that caused the
No. 10-3891                                                      5

Supreme Court to find displacement of the courts’ common-
law powers in American Electric Power, on the present state
of the record we have something close to it. In light of the
active regulatory efforts that are ongoing, we conclude that
an interim injunction would only get in the way. We stress,
however, that if the agencies slip into somnolence or if the
record reveals new information at the permanent injunction
stage, this conclusion can be revisited.


                                 I
  To justify a preliminary injunction, the plaintiff states
must show that they are likely to succeed on the merits of
their claims, that they are likely to suffer irreparable harm
without an injunction, that the harm they would suffer
without the injunction is greater than the harm that
preliminary relief would inflict on the defendants, and that
the injunction is in the public interest. Winter v. Natural Res.
Def. Council, Inc., 555 U.S. 7, 20 (2008). We will affirm the
decision to deny a preliminary injunction unless the district
court has abused its discretion. Judge v. Quinn, 612 F.3d 537,
557 (7th Cir. 2010). As usual, we review questions of fact for
clear error and questions of law de novo. Girl Scouts of
Manitou Council, Inc. v. Girl Scouts of United States of Am., Inc.,
549 F.3d 1079, 1086-87 (7th Cir. 2008).


                                II
  We begin with the states’ likelihood of succeeding on their
common law public nuisance claim. The district court
thought that the states had “at best, a very modest likelihood
of success.” For the reasons discussed below, we think that
the district court underestimated the likely merit of the
states’ claim, particularly at this early stage of the case.
                                A
  The Supreme Court recently reminded us that when it
said, “There is no federal general common law,” in Erie
6                                                   No. 10-3891

Railroad Co. v. Tompkins, 304 U.S. 64, 78 (1938), it did not
close the door on federal common law entirely. American
Electric Power, 131 S. Ct. at 2535-37. Instead, following Erie,
a “keener understanding” of federal common law
developed, under which federal courts “fill in ‘statutory
interstices,’ and, if necessary, even ‘fashion federal law’” in
areas “‘within national legislative power.’” Id. at 2535
(quoting Henry J. Friendly, In Praise of Erie - And of the New
Federal Common Law, 39 N.Y.U. L. Rev. 383 (1964)). In
American Electric Power, the Court reaffirmed a long line of
cases that have “approved federal common law suits
brought by one State to abate pollution emanating from
another State.” 131 S. Ct. at 2535-36. These decisions reach at
least as far back as the battle between Missouri and Illinois
over sewage, see Missouri v. Illinois, supra, and they have
continued from there, see Georgia v. Tennessee Copper Co., 206
U.S. 230 (1907), New York v. New Jersey, 256 U.S. 296 (1921),
New Jersey v. City of New York, 283 U.S. 473 (1931), Illinois v.
City of Milwaukee, 406 U.S. 91 (1972) (Milwaukee I), City of
Milwaukee v. Illinois, 451 U.S. 304 (1981) (Milwaukee II), and
American Electric Power, 131 S. Ct. 2527. But it has been
recognized for a much longer period that the equitable
power of the courts extends to suits to abate public
nuisances. See United Steelworkers of America v. United States,
361 U.S. 39, 60-61 (1959) (Frankfurter, J., concurring)
(assembling examples from 16th century England to the turn
of the 20th century in the United States).
  It is our federal system that creates the need for a federal
common law to govern interstate disputes over nuisances.
Tennessee Copper explains that when the states joined the
union and in so doing abandoned their right to abate foreign
nuisances by force, “they did not thereby agree to submit to
whatever might be done. They did not renounce the
possibility of making reasonable demands on the ground of
their still remaining quasi-sovereign interests; and the
alternative to force is a suit in this court.” 206 U.S. at 237. A
state that wants to bring a lawsuit attacking a nuisance
emanating from outside of its borders faces at least two legal
No. 10-3891                                                    7

difficulties: whom to sue, and what law to apply? If the
offender is another state, then the Constitution permits an
original action in the Supreme Court. U.S. CONST. Art. III sec.
2, cl. 5. Whatever the venue, applicable law is a problem: the
offending state owes no allegiance to the law of the plaintiff
state, but the plaintiff state may rightly fear protectionism if
the law of the offending state is used. Committee for
Consideration of Jones Falls Sewage Sys. v. Train, 539 F.2d 1006,
1008 (4th Cir. 1976) (en banc). Responding to this concern, the
Court has concluded that in the context of interstate
nuisances “where there is an overriding federal interest in
the need for a uniform rule of decision or where the
controversy touches basic interests of federalism,” federal
common law governs. Milwaukee I, 406 U.S. at 105 n.6. When
evaluating claims based on the federal common law of
nuisance, courts must be mindful that they do not have
“creative power akin to that vested in Congress.” American
Electric Power, 131 S. Ct. at 2536.
                               1
  The states’ public nuisance action here is based on
allegations that non-native species of carp (specifically,
bighead and silver carp) will migrate through waterworks
operated by the defendants from rivers connected to the
Mississippi into Lake Michigan and on to the other Great
Lakes. “When we deal with air and water in their ambient
and interstate aspects, there is a federal common law.”
Milwaukee I, 406 U.S. at 103. We know that this body of law
applies in a dispute about “the pollution of a body of water
such as Lake Michigan bounded, as it is, by four States,” id.
at 105 n.6. But the Court has cautioned that it has never
“held that a State may sue to abate any and all manner of
pollution originating outside its borders.” American Electric
Power, 131 S. Ct. at 2536. The Corps and the District contend
that the common law does not extend to the allegations in
this case. They stress that they are not emitting “traditional
pollutants”; all they have done, they say, is to operate
facilities in the CAWS through which invasive species
already living in local rivers might travel on their own. We
8                                                    No. 10-3891

can dismiss the latter part of this argument without much
discussion: the defendants bear responsibility for nuisances
caused by their operation of a manmade waterway between
the Great Lakes and Mississippi watersheds. That they are
not themselves physically moving fish from one body of
water to the other does not mean that their normal operation
of the CAWS cannot cause a nuisance. See, e.g.,
R ESTATEMENT (SECOND) TORTS § 834 (“One is subject to
liability for a nuisance caused by an activity, not only when
he carries on the activity but also when he participates to a
substantial extent in carrying it on.”) & cmt. (b) (defining
“activity” to include acts “that create physical conditions
that are harmful to neighboring land after the activity that
created them has ceased”).
  Similarly, we know of no rule saying that the defendants
must emit a “traditional pollutant” in order for federal
common law to apply. While it may be true that the
introduction of an invasive species of fish into a new
ecosystem does not fit the concept of nuisance as neatly as
a spill of toxic chemicals into a stream, we do not think the
Supreme Court has limited the concept of public nuisance as
much as the defendants suggest. A public nuisance is
defined as a substantial and unreasonable interference with
a right common to the general public, usually affecting the
public health, safety, peace, comfort, or convenience.
R ESTATEMENT (SECOND) T ORTS § 821B; D AN B. D OBBS, T HE
L AW OF T ORTS § 467, at 1334 (2000). It would be arbitrary to
conclude that this type of action extends to the harm caused
by industrial pollution but not to the environmental and
economic destruction caused by the introduction of an
invasive, non-native organism into a new ecosystem
(assuming that the states have correctly forecast the
depletion of the Great Lakes fishery and the corresponding
damage to the multi-billion-dollar sports fishing industry).
Public nuisance traditionally has been understood to cover
a tremendous range of subjects:
    It includes interferences with the public health, as in the
    case of a hogpen, the keeping of diseased animals, or a
No. 10-3891                                                   9

  malarial pond; with the public safety, as in the case of
  the storage of explosives, the shooting of fireworks in
  the streets, harboring a vicious dog, or the practice of
  medicine by one not qualified; with public morals, as in
  the case of houses of prostitution, illegal liquor
  establishments, gambling houses, indecent exhibitions,
  bullfights, unlicensed prize fights, or public profanity;
  with the public peace, as by loud and disturbing noises,
  or an opera performance which threatens to cause a riot;
  with the public comfort, as in the case of bad odors,
  smoke, dust and vibration; with public convenience, as
  by obstructing a highway or a navigable stream, or
  creating a condition which makes travel unsafe or
  highly disagreeable, or the collection of an inconvenient
  crowd; and in addition, such unclassified offenses as
  eavesdropping on a jury, or being a common scold.
K EETON, et al., PROSSER AND K EETON ON T ORTS § 90, at 643-45
(5th ed. 1984) (citations omitted). The Supreme Court’s
application of public nuisance principles to cases involving
shared water resources reflects this broad understanding.
For example, the Court has held that a change in one state’s
water-drainage system that causes flooding on another
state’s farms may create a public nuisance, see North Dakota
v. Minnesota, 263 U.S. 365, 374 (1923); just as the industrial
contamination of a body of water might, Arizona Copper Co.
v. Gillespie, 230 U.S. 46, 57 (1913). In this vein, American
Electric Power emphasized “that public nuisance law, like
common law generally, adapts to changing scientific and
factual circumstances.” 131 S. Ct. at 2536. The types of
invasive carp that are the concern in this case have been
designated as injurious species by the U.S. Fish and Wildlife
Service, see 50 C.F.R. § 16.13(a)(2)(v); this designation means
that it is a federal crime under the Lacy Act to transport
them around or into the United States, 16 U.S.C. §§ 3371-78.
We conclude that the federal common law of public
nuisance extends to the problem that the plaintiff states have
identified.
                              2
10                                                  No. 10-3891

   The next question, which is raised only by the Corps, is
whether the plaintiff states may state a claim based on the
federal common law of public nuisance against the United
States. The Corps asserts that “the States have shown no
basis for recognizing a federal common-law public nuisance
claim against a federal agency.” But the Corps has not
developed the argument much beyond this broad statement.
Its brief moves instead to a discussion of whether federal
common law has been displaced by congressional legislation
and whether there is any role for the courts to play when
agencies have taken concerted action to address a problem.
These are two important issues that we will explore below,
but neither point explains why a claim based on the federal
common law of public nuisance cannot move forward
against the United States. The plaintiff states have done little
to counter the Corps’s suggestion. They reply
(unresponsively, in our view) that “the federal common law
of public nuisance undoubtedly exists.”
  The implications of finding that the United States has
created a public nuisance strike us as potentially important
and complex; this is not a topic that can be thrown on the
table and then ignored. In this connection, it is telling that
the Supreme Court went out of its way in American Electric
Power to point out that it “ha[d] not yet decided whether
private citizens . . . or political subdivisions . . . of a State
may invoke the federal common law of nuisance to abate
out-of-state pollution.” 131 S. Ct. at 2536. It declined to
answer that question because it thought it best to resolve the
case on other grounds. But the Court’s statement cautions us
to tread carefully whenever we consider how far to push a
theory of federal common law. This concern is less pressing
for claims the Court has already recognized, such as those
against state or local governmental entities or private
parties. See, e.g., Missouri v. Illinois, 200 U.S. 496 (states),
Milwaukee I, 406 U.S. 91 (political subdivisions); Tennessee
Copper, 206 U.S. 230 (private citizens).
  We have not discovered any case in which the Supreme
Court has expressly authorized a public nuisance action
No. 10-3891                                                 11

against the United States in its sovereign capacity. A recent
concurring opinion in the D.C. Circuit makes the same
observation, noting that “the Court has not endorsed any
federal common-law causes of action against the
Government during the post-Erie period.” El-Shifa Pharm.
Indus. Co. v. United States, 607 F.3d 836, 853 (D.C. Cir. 2010)
(Kavanaugh, J., concurring). To understand common-law
public nuisance in a way that would exclude suits against
the United States would be faithful to the ancient origins of
nuisance, where the term described the criminal act of
infringing on the rights of the Crown, see William L. Prosser,
Private Action for Public Nuisance, 52 Va. L. Rev. 997, 998
(1966); at least during that era, no one would have
contemplated that the King or Queen could be the source of
a nuisance. Whether this sort of sovereign prerogative has
any place in modern American law, as a concept distinct
from the sovereign immunity of the United States, is a
separate question. Perhaps there is also a modern
justification for the position that the federal common law of
public nuisance cannot operate against the government: this
area of federal common law exists to provide a uniform rule
for interstate disputes that will serve the national interest,
and it may be thought illogical to say that a federal actor,
which in theory embodies the national interest, is at the
same time violating a judge-made concept of that same
interest.
  On the other hand, there are respectable arguments in
favor of applying public nuisance to the acts of federal
agencies, depending on the activity in which the agency is
engaged. We have moved far beyond the Divine Right of
Kings and the concept that the Crown can do no wrong. We
may assume that an agency’s effort to regulate private actors
in a particular area would not give rise to a claim of public
nuisance. But it is hard to see why the United States’s
ownership of a dam, power plant, or other facility should
automatically foreclose a public nuisance claim brought by
a state for harms created by the operation of that facility. If
the facility were located in and owned by State A and it was
12                                                  No. 10-3891

damaging State B, then State B would be entitled to assert a
common-law claim against State A (or one of its
subdivisions or private citizens). Our case offers a good
illustration of the point: the Corps and the District together
operate facilities that are allegedly on the verge of creating
a nuisance in waters of the plaintiff states; why should the
plaintiffs be able to state a claim against the District but not
the Corps?
   The possible inconsistencies that would be created by such
a rule may be the reason that no court has expressed concern
about the appearance of the Tennessee Valley Authority – a
federally owned entity that was created by Congress and
acts like a private corporation – as a defendant in a public
nuisance lawsuit. See American Electric Power, 131 S. Ct. 2527;
North Carolina ex rel. Cooper v. TVA, 615 F.3d 291 (4th Cir.
2010); North Carolina ex rel. Cooper v. TVA, 515 F.3d 344 (4th
Cir. 2008). In fact, out of all public nuisance decisions we
have identified from either the Supreme Court or the Courts
of Appeals that involve a federal agency as a defendant,
none contains a whisper of discussion about whether the
claim runs against the United States. In addition to the cases
just mentioned, see Middlesex Cnty. Sewerage Auth. v. National
Sea Clammers Ass’n, 453 U.S. 1, 4 & n.3 (1981) (claims against
the Environmental Protection Agency and the Corps);
Committee for Consideration of Jones Falls Sewage Sys., 539 F.2d
1006 (claims against the EPA); Massachusetts v. U.S. Veterans
Admin., 541 F.2d 119 (1st Cir. 1976) (claims against the
Veterans Administration). Whether the plaintiffs’ common-
law action can proceed against the Corps is a question that
may well require attention as this case proceeds. Given the
parties’ cursory exposition of the issue and our ultimate
conclusion that preliminary relief is not warranted, we find
it unnecessary to say more at this point. (We see this as a
question relating to the plaintiffs’ ability to state a claim; it
does not implicate the court’s jurisdiction, and so there is
nothing to prevent our declining to reach it.) For now, we
will assume that the states’ federal common-law claim may
proceed against all of the defendants.
No. 10-3891                                                  13

                               B
  The defendants argue that two additional obstacles also
diminish the states’ likelihood of succeeding on their public
nuisance claim. The first concerns the sovereign immunity
of the United States. The Corps contends that even if it
makes sense to apply public nuisance principles against the
United States, the Corps is nevertheless not subject to suit
because the United States has not waived its sovereign
immunity for this kind of claim. The second argument,
which we address below, is that congressional regulation of
the invasive carp problem has displaced any role for federal
common law.
  “Absent a waiver, sovereign immunity shields the Federal
Government and its agencies from suit.” F.D.I.C. v. Meyer,
510 U.S. 471, 475 (1994). The Corps takes the position that
there is no such waiver of immunity for lawsuits against the
United States that seek declaratory and injunctive relief
based on a federal common-law tort. Whether this is correct
depends on the interaction between section 702 of the APA
and the Federal Tort Claims Act (FTCA), 28 U.S.C. § 1346(b).
  We begin with a look at the APA. Section 702 reads as
follows:
  A person suffering legal wrong because of agency
  action, or adversely affected or aggrieved by agency
  action within the meaning of a relevant statute, is
  entitled to judicial review thereof. An action in a court
  of the United States seeking relief other than money
  damages and stating a claim that an agency or an officer
  or employee thereof acted or failed to act in an official
  capacity or under color of legal authority shall not be
  dismissed nor relief therein be denied on the ground
  that it is against the United States or that the United
  States is an indispensable party.
5 U.S.C. § 702. “The first and second sentences of § 702 play
quite different roles.” Veterans for Common Sense v. Shinseki,
644 F.3d 845, 866 (9th Cir. 2011). The first supplies a right to
14                                                   No. 10-3891

seek review of agency action; the second, added by the 1976
amendments to the statute, provides a waiver of sovereign
immunity. Id. The waiver covers actions that seek specific
relief other than money damages; this aptly describes the
plaintiffs’ claim for declaratory and injunctive relief. See
Blagojevich v. Gates, 519 F.3d 370, 371-72 (7th Cir. 2008)
(noting that § 702 “waived sovereign immunity for most
forms of prospective relief”); see also Bowen v. Massachusetts,
487 U.S. 879, 893 (1988) (construing § 702’s waiver broadly
and remarking that “complaints [for] declaratory and
injunctive relief . . . [are] certainly not actions for money
damages”); Veterans for Common Sense, 644 F.3d at 864-65.
Moreover, the waiver in § 702 is not limited to claims
brought pursuant to the review provisions contained in the
APA itself. The waiver applies when any federal statute
authorizes review of agency action, as well as in cases
involving constitutional challenges and other claims arising
under federal law. Blagojevich, 519 F.3d at 372; Czerkies v. U.S.
Dep't of Labor, 73 F.3d 1435, 1437-38 (7th Cir. 1996) (en banc);
see also Veterans for Common Sense, 644 F.3d at 867-68;
Trudeau v. Federal Trade Comm’n, 456 F.3d 178, 186-87 (D.C.
Cir. 2006); United States v. City of Detroit, 329 F.3d 515, 520-21
(6th Cir. 2003) (en banc); Jaffee v. United States, 592 F.2d 712,
718 (3d Cir. 1979).
  Although the United States has argued from time to time
that the “final agency action” requirement of § 704 limits the
waiver of immunity in § 702, it has not prevailed on that
ground. E.g., Veterans for Common Sense, 644 F.3d at 866-68;
Trudeau, 456 F.3d at 186-87. The Corps wisely does not take
that position here; as the Ninth Circuit explained recently,
the conditions of § 704 affect the right of action contained in
the first sentence of § 702, but they do not limit the waiver of
immunity in § 702+s second sentence. Veterans for Common
Sense, 644 F.3d at 866-68. The only limitation on § 702 that
requires our attention is the clause that says, “Nothing
herein . . . confers authority to grant relief if any other
statute that grants consent to suit expressly or impliedly
forbids the relief which is sought,” 5 U.S.C. § 702(2), which
No. 10-3891                                                   15

Congress added to the statute at the same time that it
introduced the waiver of sovereign immunity, see Pub. L.
94-574, 90 Stat. 2721 (Oct. 21, 1976). Pointing to this
provision, the Corps frames an argument by negative
implication: it says that when Congress enacted the FTCA in
1946, it did so against a backdrop of no tort liability for the
United States; the FTCA waives the government’s sovereign
immunity in suits for money damages to the extent that a
private person would be held liable under applicable state
tort law, see 28 U.S.C. § 1346(b)(1); Smith v. United States, 507
U.S. 197, 201-02 (1993); Parrott v. United States, 536 F.3d 629,
635 (7th Cir. 2008); but while the FTCA authorizes actions
for damages, it says nothing at all about injunctive relief;
thus, the FTCA implicitly prohibits injunctive relief in tort
suits against the United States; and because of § 702(2), the
Corps’s argument concludes, the plaintiffs cannot use the
APA’s wavier of immunity to assert a common-law tort
claim against the United States.
  That argument reads too much into congressional silence.
The FTCA authorizes various tort claims for damages
against the government to the extent that state law would
provide relief, and it spells out a number of explicit
exceptions. E.g., 28 U.S.C. § 2674 (barring punitive damages
and interest before judgment); id. § 2680 (limiting the waiver,
among other circumstances, where the alleged tort concerns
the government’s enforcement of a statute or a discretionary
function). There is nothing in the statute suggesting that
Congress meant to forbid all actions that were not expressly
authorized. To the contrary, section 702(2) requires evidence,
in the form of either express language or fair implication,
that Congress meant to forbid the relief that is sought. The
Corps’s effort to transform silence into implicit prohibition
would seriously undermine Congress’s effort in the APA to
authorize specific relief against the United States. When
Congress amended the APA in 1976 it gave every indication
that it intended to provide specific relief for all nonstatutory
claims against the government. See Trudeau, 456 F.3d at
186-87 (noting that all the reports from Congress “identified
16                                                  No. 10-3891

as the measure’s clear purpose elimination of the sovereign
immunity defense in all equitable actions” and that “the
Senate Report plainly indicated that Congress expected the
waiver to apply to nonstatutory actions”) (internal quotation
marks and alterations removed); Jaffee, 592 F.2d at 718-19
(outlining the reasons for the amendments to § 702, the
concern that some executive departments were hiding
behind their immunity, and concluding, “It was therefore
precisely for equitable actions under section 1331 that
Congress enacted the amendments to section 702“).
  The D.C. Circuit has read the Tucker Act, which it
interprets as the exclusive remedy for contract claims
against the government, to include an implicit prohibition
against specific relief in contract actions against the United
States and thus to prevent reliance on the APA’s waiver of
immunity in such cases. Sharp v. Weinberger, 798 F.2d 1521,
1523-24 (D.C. Cir. 1986) (Scalia, J.). But the same court has
since decided that, whatever the unspoken effect of the
Tucker Act may be, the FTCA does not contain a comparable
implicit ban against specific relief in tort cases against the
government, and thus that plaintiffs in such cases may take
advantage of the waiver in § 702 of the APA. U.S. Info.
Agency v. Krc, 989 F.2d 1211, 1216 (D.C. Cir. 1993). To the
same effect, we recently explained that while “[t]he tort
claims act doesn’t authorize equitable relief . . . . the
Administrative Procedure Act does,” and we went on to say
that a plaintiff asserting a tort claim against a federal agency
could take advantage of the APA to obtain equitable relief.
Robinson v. Sherrod, 631 F.3d 839, 841 (7th Cir. 2011).
   If that were not reason enough to reject the Corps’s
immunity defense, there is more. By its terms, the FTCA
does not apply to any federal common-law tort claim, no
matter what relief is sought. As the Corps itself points out,
state tort law – not federal law – is the source of substantive
liability under the FTCA. See Meyer, 510 U.S. at 478-79;
Sobitan v. Glud, 589 F.3d 379, 388-89 (7th Cir. 2009); cf. Smith,
507 U.S. at 198 (no FTCA claim for tort committed in
Antarctica, a sovereignless entity not subject to either state
No. 10-3891                                                    17

law or the law of a foreign country). The states’ tort claim is
based entirely on federal common law, and so the claim
would not be cognizable under the FTCA in the first place.
Meyer, 510 U.S. at 478. And if the FTCA could never apply to
the type of claim advanced, then there is no reason to think
that it implicitly forbids a particular type of relief for a claim
outside its scope. For all these reasons, we conclude that the
waiver contained in § 702 of the APA subjects the Corps to
the plaintiffs’ common-law claims for declaratory and
injunctive relief.
                                C
  The Corps and the District next contend that congressional
regulation has displaced as a matter of law the federal
common law on which the states rely. The district court
rejected this argument on the ground that Congress had not
done enough about the threat of invasive carp to qualify for
displacement of the federal common-law claim. The
defendants say this was error. As they see things, it is
enough that Congress has passed legislation to stop the carp
and that federal and state agencies are hard at work to
address the problem. Because the parties disagree about the
effect of American Electric Power and the way in which the
displacement analysis should proceed, we begin with a few
important principles.
  The doctrine of displacement rests on the premise that
federal common law is subject to the paramount authority of
Congress. New Jersey v. New York, 283 U.S. 336, 348 (1931);
see also American Electric Power, 131 S. Ct. at 2537 (“[I]t is
primarily the office of Congress, not the federal courts, to
prescribe national policy in areas of special federal
interest.”). “‘[W]hen Congress addresses a question
previously governed by a decision rested on federal
common law . . . the need for such an unusual exercise of
law-making by federal courts disappears.’” American Electric
Power, 131 S. Ct. at 2537 (quoting Milwaukee II, 451 U.S. at
314). Displacement focuses on the relation between Congress
and the federal courts – it is not a doctrine that is concerned
18                                                 No. 10-3891

with the relation between the federal courts and the
executive branch. This is a distinction often neglected by
courts, as well as by the parties to this case. Whether federal
courts can or should play a role in the face of comprehensive
agency action is a critical issue, which we address below, but
executive action or lack thereof does not affect the
displacement analysis. See American Electric Power, 131 S. Ct.
2538-39 (rejecting the argument that an agency must have
taken action before common law is displaced and explaining
that the EPA’s outright refusal to regulate emissions would
not create a role for federal common law because “the
delegation [of regulatory authority from Congress to the
agency] is what displaces federal law”); Milwaukee II, 451
U.S. at 317-18, 324 n.18 (concluding that displacement had
occurred because “Congress . . . has occupied the field
through the establishment of a comprehensive regulatory
program supervised by an expert administrative agency,”
regardless of how thoroughly the agency has implemented
that program) (emphasis added). Congress’s decision to
assign a particular problem to an executive agency or its
description of an agency’s role in addressing a problem may
be evidence of displacement, but the ebb and flow of agency
action neither diminishes nor increases the role of federal
common law. The important displacement question is
whether Congress has provided a sufficient legislative
solution to the particular interstate nuisance here to warrant
a conclusion that this legislation has occupied the field to the
exclusion of federal common law.
  We readily concede that Congress has not been mute on
the subject of the carp, but that simply underscores the
critical question: how much congressional action is enough?
In their supplemental memoranda filed after American
Electric Power was decided, the defendants seize upon the
statement from the opinion that we quoted above – that “the
delegation is what displaces federal law.” 131 S. Ct. at 2538.
Their view is that all Congress must do to displace federal
law is to indicate its intention to delegate a particular
problem to an executive agency. They read American Electric
No. 10-3891                                                 19

Power as an enlargement of whatever displacement doctrine
existed previously. But the defendants have taken the
Court’s statement out of context. The Court in that passage
was responding to an argument that an agency must have
acted pursuant to its statutory power before federal common
law is displaced. See id. at 2538-39. The Court explained that
this was not the case and that it is congressional action, not
executive action, that guides the displacement analysis. In so
ruling the Court did not establish a new test based solely on
Congress’s delegation of regulatory power; it simply pointed
out that delegation is one type of congressional action that
is evidence of displacement. “The test for whether
congressional legislation excludes the declaration of federal
common law,” the Court said, “is simply whether the statute
‘speak[s] directly to [the] question’ at issue.” Id. at 2537
(quoting Mobil Oil Corp. v. Higginbotham, 436 U.S. 618, 625
(1978), and citing Milwaukee II, 451 U.S. at 315, and County of
Oneida v. Oneida Indian Nation of N.Y., 470 U.S. 226, 236-37
(1985)). Importantly, while Congress must have spoken to
the particular question at issue, it is not necessary for us to
find the same manifest congressional purpose that we would
require in an analysis of whether Congress has preempted
state law. Id. at 2537.
  Earlier federal nuisance cases provide additional insight
into the level of congressional action that is sufficient to
displace federal common law. In Milwaukee I, where Illinois
sued Milwaukee and other cities to stop them from dumping
sewage into Lake Michigan, the Court decided that the
federal common law of public nuisance had not been
displaced, despite the fact that Congress had by that time
“enacted numerous laws touching interstate waters.” 406
U.S. at 101-07. Laws that touched on the issue at hand were
not enough, and thus the common law action could move
forward. At the same time, however, the Court
foreshadowed that federal legislation “may in time pre-empt
the field of federal common law of nuisance.” Id. at 107. Six
months after Milwaukee I, Congress passed sweeping
amendments to the Federal Water Pollution Control Act
20                                                  No. 10-3891

(FWPCA), and nine years after its first decision, the Court
decided in Milwaukee II that those amendments displaced
federal common law in the area. 451 U.S. at 317-18. The
Court viewed the amended statute as “a comprehensive
regulatory program supervised by an expert administrative
agency,” and it noted that under that regulatory program
“[e]very point source discharge is prohibited unless covered
by a permit.” Id. at 317-18. This permitting requirement
brought every potential interstate water polluter within
Congress’s administrative scheme; any discharge had to be
done with the permission of the EPA or a qualifying state
agency; and there were enforcement options available when
polluters failed to meet the conditions of permits that had
been issued. See id. at 310-11.
  Most recently, American Electric Power held “that the Clean
Air Act and the EPA actions it authorizes displace any
federal common law right to seek abatement of
carbon-dioxide emissions from fossil-fuel fired power
plants.” 131 S. Ct. at 2537. The Court found it important that
the Clean Air Act requires the EPA to identify and establish
performance standards for all carbon-dioxide emitters; the
statute also “provides multiple avenues for enforcement,”
which include state agencies (operating under power
delegated by EPA), the EPA itself, criminal proceedings
against violators, and private enforcement in the event that
the EPA or the states fail to regulate emissions. If the EPA
has not acted, states and private parties may petition the
agency for a rulemaking, after which parties have a right to
review in federal court. Id. at 2537-38. The Court concluded
with the observation that “[t]he Act itself thus provides a
means to seek limits on emissions of carbon dioxide from
domestic power plants—the same relief the plaintiffs seek by
invoking federal common law. We see no room for a parallel
track.” Id. at 2538.
  For better or for worse, congressional efforts to curb the
migration of invasive species, and of invasive carp in
particular, have yet to reach the level of detail one sees in the
air or water pollution schemes. In 1990, Congress passed the
No. 10-3891                                                 21

Aquatic Nuisance Prevention and Control Act in an attempt
to stop the spread of zebra mussels and other nuisance
species. See 16 U.S.C. §§ 4701 et seq. That statute established
the Aquatic Nuisance Species Task Force and gave it the job
of studying invasive species and implementing a program
“to prevent introduction and dispersal of aquatic nuisance
species” in the United States. See id. § 4722. In 1996, the
National Invasive Species Act amended the 1990 law and
directed the Corps and the task force to “investigate and
identify environmentally sound methods for preventing and
reducing the dispersal of aquatic nuisance species between
the Great Lakes [basin] and the Mississippi River [basin]
through the Chicago River Ship and Sanitary Canal,”
including any methods that could be incorporated in the
normal operation of the CAWS. Id. § 4722(i)(3)(A). This
mandate led to the construction of an underwater electric
barrier in the Chicago Ship and Sanitary Canal. The barrier
sits just upstream of the point where the CAWS empties into
the Des Plaines River; it is designed to deter fish from
moving in either direction through the canal. In 2003 the
Corps, relying on the continuing authority given to the
Secretary of the Army in 33 U.S.C. § 2309a, began
construction of a second barrier next to the first. The barrier
projects received an additional influx of cash from the
District of Columbia Appropriations Act of 2005, Pub. L.
108-335, § 345, 118 Stat. 1352 (Oct. 18, 2004). In 2007,
Congress passed the Water Resources Development Act,
Pub. L. No. 110-114, § 3061(b)(1), 121 Stat. 1121 (Nov. 8,
2007), which allowed the Corps to upgrade its first barrier
and officially authorized the construction of the already-in-
progress second barrier. Finally, the Corps received more
money to complete a third barrier as part of the American
Reinvestment and Recovery Act of 2009.
  Sections 3061(b) and (d) of the Water Resources
Development Act of 2007, supra, instructed the Corps to
undertake two studies: a short-term examination of how the
electric barrier systems might more effectively stop invasive
species (this is the Efficacy Study, which so far consists of
22                                                  No. 10-3891

four interim reports, see http://www.lrc.usace.army.mil/
AsianCarp/efficacy.htm); and a long-term study of how the
Mississippi and Great Lakes basins might be separated on a
more permanent basis (this is the Great Lakes and
Mississippi River Interbasin Study or “GLMRIS,” see
http://glmris.anl.gov). In an appropriations bill for fiscal year
2009, Congress provided that “the Secretary of the Army
shall implement measures recommended in the efficacy
study, or provided in interim reports, authorized under
section 3061 of the Water Resources Development Act of
2007 . . . with such modifications or emergency measures as
the Secretary of the Army determines to be appropriate, to
prevent aquatic nuisance species from bypassing the
Chicago Sanitary and Ship Canal Dispersal Barrier Project
referred to in that section and to prevent aquatic nuisance
species from dispersing into the Great Lakes.” Energy and
Water Development and Related Agencies Appropriations
Act 2010, Pub. L. No. 111-85, § 126, 123 Stat. 2845, 2853 (Oct.
28, 2009). This authority – referred to informally as the
Section 126 power — is set to expire on September 30, 2011.
Department of Defense and Full-Year Continuing
Appropriations Act 2011, Pub. L. No. 112-10, §§ 1101(a)(2),
1104, 1106, 125 Stat. 38, 103 (Apr. 15, 2011). Add to these
measures the appropriation of funds so that the Corps can
ensure proper operation of the CAWS, e.g., Pub. L. No. 98-63,
97 Stat. 301, 311 (July 30, 1983); Pub. L. No. 97-88 § 107, 95
Stat. 1135, 1137 (Dec. 4, 1981); Pub. L. No. 79-525, 60 Stat.
634, 636 (July 24, 1946), and one has the whole of Congress’s
efforts to stop invasive species from moving through the
CAWS. Recent legislative proposals targeted at halting
invasive carp have failed in both Houses. E.g., Close All
Routes and Prevent Asian Carp Today Act of 2010 (CARP
ACT), H.R. 4472, S. 2946.
  Although this legislation demonstrates that Congress is
aware of the problem of invasive species generally, and carp
in particular, it falls far short of the mark set by the Clean
Air Act or the Federal Water Pollution Control Act.
Congress has not passed any substantive statute that speaks
No. 10-3891                                                  23

directly to the interstate nuisance about which the states are
complaining. Most of the laws that we have summarized
appropriate funds to the Corps for routine maintenance of
the CAWS or for the electric barrier project. Apart from
requiring the construction of these barriers and giving the
Secretary of the Army temporary power to implement
various recommendations, Congress has ordered agencies
(or, more commonly, informal task forces composed of
various executive actors) only to study the invasive species
problem and propose solutions. Beyond that, neither the
Corps nor any other agency has been empowered actively to
regulate the problem of invasive carp, and Congress has not
required any agency to establish a single standard to deal
with the problem or to take any other action. The narrow
delegation that has taken place bears little resemblance to
the regulatory power that the EPA wields under the Clean
Air Act. Tellingly, Congress has not provided any
enforcement mechanism or recourse for any entity or party
negatively affected by the carp, and there is certainly no
recourse to the courts under the minimal scheme that has
been established. The district court was correct that the
current state of congressional regulation is much closer to
the situation examined in Milwaukee I – and perhaps even
less extensive than that – than the regimes reviewed in
Milwaukee II or American Electric Power.
                               D
  With these important preliminary questions out of the
way, we are at last ready to consider whether the plaintiff
states have presented enough evidence in support of their
nuisance claim to establish that they are likely to succeed on
the merits. The district court thought that the states failed to
demonstrate more than a minimal chance of success. Before
this court, the states contend that the district court
misunderstood the elements of public nuisance. They point
to the district judge’s statement that the tort “contemplates
an active – or, at least, an imminent – threat of injury” as
evidence of that error. In their view, all they must show to
win final relief in a trial on the merits is that there is a
24                                                 No. 10-3891

“significant threat” that the nuisance will occur. This is a
distinction without a difference; the district court correctly
understood the law of public nuisance. Nonetheless, for
different reasons we think that the district judge may have
underestimated the states’ likelihood of success. We will
elaborate on this point after a brief review of the governing
law.
                               1
   The district court began with the definition of public
nuisance found in the Restatement (Second) of Torts, which has
been a common reference point for courts considering cases
arising under federal common law. See Connecticut v.
American Electric Power Co., Inc., 582 F.3d 309, 351 & n.28 (2d
Cir. 2009), rev’d on other grounds, American Electric Power, 131
S. Ct. 2527 (explaining that “[t]he Restatement definition of
public nuisance has . . . been used in . . . federal cases
involving the federal common law of nuisance . . . and the
Restatement principles have served as the backbone of state
nuisance law”). The Restatement provides that “A public
nuisance is an unreasonable interference with a right
common to the general public,” R ESTATEMENT (SECOND) OF
T ORTS § 821B(1), and it goes on to explain that conduct meets
this standard when it interferes significantly with the public
health, safety, peace, comfort, or convenience, id. §
821B(2)(a). We described above the reasons why the federal
common law of public nuisance is available to redress the
type of harm that the states have alleged. And all sides agree
that if invasive carp were to achieve a sustainable
population in the Great Lakes, the environmental and
economic impact would qualify as an unreasonable
interference with a public right. As the district court noted,
the Corps and other agencies have repeatedly and publicly
acknowledged the seriousness of the problem. The Corps,
for example, has said that invasive carp “have the potential
to damage the Great Lakes and confluent large riverine
ecosystems,” and that it regards “[t]he prevention of an
inter-basin transfer of bighead and silver carp from the
Illinois River to Lake Michigan [as] paramount in avoiding
No. 10-3891                                                     25

ecologic and economic disaster.” As a result, the central
question on the merits of the states’ public nuisance claim
will be whether the harm that the states have described is
sufficiently close to occurring that the courts should order
the defendants to take some new action that will be effective
to abate the public nuisance. We stress at the outset an
important point to which we will return: this question is one
that will be resolved after a full trial on the merits, rather
than at this preliminary stage of the case.
   A court may grant equitable relief to abate a public
nuisance that is occurring or to stop a threatened nuisance
from arising. See Tennessee Copper, 206 U.S. at 238-39
(requiring the plaintiff to show that a defendant’s actions
“cause and threaten damage”). In Missouri v. Illinois, 200 U.S.
at 518, the Court wrote that the threatened harm underlying
the nuisance claim “must be shown to be real and
immediate.” We have read the Court’s cases to say that
“[t]he elements of a claim based on the federal common law
of nuisance are simply that the defendant is carrying on an
activity that is causing an injury or significant threat of
injury to some cognizable interest of the complainant,”
Illinois v. City of Milwaukee, 599 F.2d 151, 165 (7th Cir. 1979),
rev’d on other grounds, Milwaukee II, 451 U.S. 304. Additional
statements about averting threatened nuisances appear in
the Restatement, see RESTATEMENT (SECOND) T ORTS § 821B
cmt. (i) (“[F]or damages to be awarded [in public nuisance
cases] significant harm must have been actually incurred,
while for an injunction harm need only be threatened and
need not actually have been sustained at all.”); id. § 821F
cmt. (b) (“[E]ither a public or a private nuisance may be
enjoined because harm is threatened that would be
significant if it occurred.”), and in other treatises, see, e.g., 5
J. POMEROY, A T REATISE ON E QUITY JURISPRUDENCE AND
E QUITABLE REMEDIES, § 1937 (§ 523), at 4398 (2d ed. 1919)
(noting that while “a mere possibility of a future nuisance
will not support an injunction,” relief will be warranted
when “the risk of its happening is greater than a reasonable
man would incur”).
26                                                  No. 10-3891

   The plaintiffs believe that the district court’s “imminent
threat” requirement is inconsistent with these principles, but
we do not share that view. The district court reproduced
verbatim the elements of the claim as we described them in
Illinois v. City of Milwaukee, supra. Its discussion of
“immediacy” did nothing more than flesh out the Court’s
requirement of a “real and immediate” threat in public
nuisance cases. There is no meaningful legal difference for
purposes of the ultimate resolution of a public nuisance
claim between a threatened nuisance that is “imminent” and
one that is “immediate,” “significant,” “real,” an
“unreasonable risk,” or anything similar. The job of a court
considering the merits of a public nuisance claim is simply
to determine whether the activity complained of is a
nuisance and, if so, whether it is sufficiently close to
occurring that equitable relief is necessary to prevent it from
happening.
                               2
  We part company with the district court when it comes to
the assessment of the states’ likelihood of success on the
merits. Here we think it critical to bear in mind the
difference between preliminary or interim relief, on the one
hand, and permanent relief, on the other. The principles that
we just reviewed relate to the ultimate outcome of a public
nuisance proceeding. This case has not yet reached that
stage, and one consequence of its preliminary posture is that
the states were not required to prove that they will
ultimately win on the merits in order to secure preliminary
relief.
  “The propriety of preliminary relief and resolution of the
merits are of course significantly different issues.” Parents
Involved in Cmty. Sch. v. Seattle Sch. Dist. No. 1, 551 U.S. 701,
721 n.10 (2007) (internal quotation marks omitted). This is
the reason why findings made at the preliminary injunction
stage do not bind the district court as the case progresses. Cf.
Guaranty Bank v. Chubb Corp., 538 F.3d 587, 591 (7th Cir.
2008). The most significant difference between the
No. 10-3891                                                    27

preliminary injunction phase and the merits phase is that a
plaintiff in the former position needs only to show “a
likelihood of success on the merits rather than actual
success.” Amoco Prod. Co. v. Village of Gambell, 480 U.S. 531,
546 n.12 (1987); cf. Chathas v. Local 134 Int’l Bhd. of Elec.
Workers, 233 F.3d 508, 513 (7th Cir. 2000) (“A plaintiff cannot
obtain a permanent injunction merely on a showing that he
is likely to win when and if the merits are adjudicated.”). In
some cases, it is necessary to expedite an ultimate decision,
and so courts sometimes consolidate the preliminary
injunction hearing with the trial on the merits. See FED. R.
C IV. P. 65(a)(2). But where such consolidation has not taken
place – and it has not here – and the question is the
propriety of preliminary relief, the Supreme Court has
warned against “improperly equat[ing] ‘likelihood of
success’ with ‘success’ . . . .” University of Texas v. Camenisch,
451 U.S. 390, 394 (1981); see also Meridian Mut. Ins. Co. v.
Meridian Ins. Group, Inc., 128 F.3d 1111, 1119 (7th Cir. 1997).
This is in keeping with the often-repeated rule that the
threshold for establishing likelihood of success is low. E.g.,
Cooper v. Salazar, 196 F.3d 809, 813 (7th Cir. 1999); Brunswick
Corp. v. Jones, 784 F.2d 271, 275 (7th Cir. 1986).
  We are concerned that the district court here may have
lost sight of this distinction. By applying directly the law of
public nuisance, the judge seems to have required the
plaintiff states actually to show that they were entitled to
permanent injunctive relief during the preliminary
injunction hearing. The court concluded its discussion of the
threat posed by invasive carp, for example, by saying that
the states “ha[d] not made a convincing case” that the fish
had pushed into the CAWS in significant numbers; and it
said that the plaintiffs had not “shown that the fish [are]
anywhere near . . . establishing a population in Lake
Michigan.” Because the states had not yet shown that the
threat of nuisance was great enough in the final analysis to
warrant an injunction to abate it, the district court seems to
have assumed that they had also failed to show enough to
obtain preliminary relief. To demonstrate the requisite
28                                                 No. 10-3891

likelihood of success, however, the states needed only to
present a claim plausible enough that (if the other
preliminary injunction factors cut in their favor) the entry of
a preliminary injunction would be an appropriate step. The
preliminary injunction, after all, is often seen as a way to
maintain the status quo until merits issues can be resolved at
trial. By moving too quickly to the underlying merits, the
district court required too much of the plaintiffs and,
correspondingly, gave too little weight to the strength of
their claim at this stage of the case.
                               3
  We also question the inferences drawn by the district court
from the facts that it so carefully found after evaluating five
days of hearings, which included the testimony of expert
witnesses and volumes of written materials on complex
scientific and engineering issues. There is very little to
criticize about the court’s factual findings themselves. For
instance, the district judge’s decision to admit the expert
testimony of Dr. David Lodge, who has been hired by the
Corps and who testified for the states at the preliminary
injunction hearing about his efforts to track invasive carp
through the use of environmental DNA (eDNA) testing,
reflects a proper application of Federal Rule of Evidence 702.
(We agree that any lack of peer review of Dr. Lodge’s work
would go to the weight of his testimony, not to the court’s
ability to consider it. Moreover, the situation will be
different at the merits phase, given Dr. Lodge’s recent
publication of his research. See Christopher L. Jerde,
Andrew R. Mahon, W. Lindsay Chadderton & David M.
Lodge, “Sight Unseen” Detection of Rare Aquatic Species Using
Environmental DNA, 4 Conservation Letters 150 (April/May
2011).) We also see nothing to criticize in the district court’s
assessment that the electric barriers built by the Corps near
the intersection of the Chicago Sanitary and Ship Canal and
the Des Plaines River seem to have at least some deterrent
effect on the movement of invasive carp toward the Great
Lakes. In addition, we consider it significant, as the district
judge did, that efforts to detect carp by techniques including
No. 10-3891                                                29

netting, so-called electrofishing, and rotenone poisoning,
have led to few signs of the carp.
    Along the same lines, the district court was right to take
into account the results of eDNA testing. Despite its
skepticism about the reliability of the technique and its
concern that the state of eDNA science “did not permit a
reasonable inference that live Asian carp are in the [CAWS]
. . . in numbers that present an imminent threat,” the court
acknowledged that the eDNA evidence lent some support to
the conclusion that there may be invasive carp above (i.e.
lakeside of) the Corps’s electric barriers. Although we are
less skeptical of the science than the district court, we too
believe that caution in drawing inferences from the existence
of carp DNA in the water is warranted. The eDNA
technique, which tests water samples for markers matching
a particular species, has a number of shortcomings: it is
difficult, if not impossible, to know definitively whether a
positive result signals a living specimen above the barrier
(DNA may be shed by a dead or distant fish); a positive test
does not reveal the number of live fish; and negative results
do not necessarily signal the absence of carp. Efforts to
corroborate eDNA results with traditional methods of
capturing fish have not been successful thus far. On the
other hand, the evidence is worth something. The eDNA
technique detects carp when the fish are present in small
numbers and in situations where the other fishing methods
we described above might scare them away or simply miss
them, and the large number of negative test results make
sense given the sensitivity of the technique. In addition, the
Corps and other agencies have voted with their feet: they
have been using eDNA tests to manage the invasive carp
crisis, and they have said that this testing will continue.
(This is undoubtedly why the private intervenor-defendants
are the primary critics of this methodology.) If the tests are
good enough for expert agencies, it is hard to see why we
should flatly forbid their consideration. A January 2011
report on eDNA sampling conducted in 2010 showed
positive eDNA results in approximately a dozen locations
30                                                  No. 10-3891

throughout the CAWS, and experts have opined that these
results indicate the presence of carp at multiple locations in
the CAWS. On July 29, 2011, federal officials announced that
they would begin daily efforts to find invasive carp around
Lake Calumet, after multiple rounds of testing revealed carp
DNA in that area. See Asian Carp Regional Coordinating
Com m ittee, Press Release, July 29, 2011,
http://asiancarp.org/news/asian-carp-regional-coordinating-
committee-to-begin-intensive-monitoring-in-lake-calumet-
in-response-to-environmental-dna-results; Tammy Webber,
Feds to Step Up Hunt for Asian Carp Near Chicago, Chicago
Tribune, July 29, 2011. The district court thought that this
evidence, in combination with the discovery of two invasive
carp specimens (one dead and one living) in the CAWS,
supported a theory that invasive carp are present in the
CAWS in “low numbers.” This conclusion was reasonable.
The carp may even be present in greater numbers, but for
present purposes we do not need any more precision.
  Our greatest hesitation with respect to the district court’s
findings is over its conclusion that “it is far from certain that
Asian carp can survive and reproduce in the Great Lakes.”
Given the record that was before Judge Dow, this prediction
may have been sound at the time he ruled. The situation has
been evolving rapidly since the preliminary injunction
hearing, however, and so we think it worth mentioning that
the newest publicly available evidence suggests that when
and if the time comes, the carp are unlikely to have trouble
establishing themselves in the Great Lakes. Before the
district court there was testimony reflecting great
uncertainty about how easily the carp could live and
reproduce in this new habitat. A species typically requires
multiple introductions before it takes root in a new
ecosystem, and there has been a substantial debate, reflected
in the literature, about whether the food supply and other
features of the Great Lakes could support the carp. See
generally Sandral L. Cooke & Walter R. Hill, Can Filter-
Feeding Asian Carp Invade the Laurentian Great Lakes? A
Bioenergetic Modelling Exercise, 55 Freshwater Biology 2138
No. 10-3891                                                   31

(2010); Cynthia S. Kolar & David M. Lodge, Ecological
Predictions and Risk Assessment for Alien Fishes in North
America, 298 Science 1233 (2002). On April 28, 2011, however,
the Obama Administration presented two pieces of what it
called “bad news” at a meeting in Chicago on invasive carp:
first, it said that while it was once thought that the carp
could not establish breeding populations in Lake Michigan
because of the low levels of plankton (the carp’s normal food
source) in the water, new evidence suggests that the fish will
happily switch from eating plankton to consuming the green
algae that now covers the lake floor (thanks to another
invasive species, the zebra mussel); and (2) while experts
had thought the carp need coastal rivers between 30 and 60
miles long to spawn, it turns out they can make do with
much shorter breeding grounds. See, e.g., Asian Carp Possibly
Hardier than Once Thought, Chicago Tribune, Apr. 28, 2011.
At this point, therefore, we must assume that once in the
Great Lakes, the invasive carp would make it their home.
   We need not explore the factual record further. As we
have said, our review of the district court’s findings is
deferential, and we see nothing that demands correction.
The critical point is that this record is not a static thing. The
district court will undoubtedly have more evidence before
it when it is time to rule on the request for a permanent
injunction, and we are confident that the court will keep its
mind open to the implications of any new information. For
purposes of assessing the need for preliminary relief, the
court relied on its findings that at best a limited number of
invasive carp were present in the CAWS and its observation
that the so-called invasion front was approximately 30 miles
downstream of the CAWS (60 miles from Lake Michigan) as
of the spring of 2009. On this basis, it reached the conclusion
that while the potential for damage to the Great Lakes is
high, the problem had not advanced far enough to present
a threat to the plaintiff states. From that it drew the
conclusion that the states had shown little likelihood of
success on the merits.
  It is that final step that gives us trouble. As the district
32                                                             No. 10-3891

court rightly noted, the magnitude of the potential harm
here is tremendous, and the risk that this harm will come to
pass may be growing with every passing day. (It certainly
has grown since the ill-fated day around 1970 when the carp
escaped from various aquaculture facilities and began their
march up the Mississippi River. See generally Wisconsin
Dep’t of Nat. Res., Bighead and Silver Carp
( H y p o p h t h a l m i c h t h y s n o bi l i s a n d H . m o l i t r ix ) ,
http://dnr.wi.gov/invasives/fact/asian_carp.htm.) Given the
magnitude of the harm, we are inclined to give the benefit of
the doubt to the states on the question whether they have
shown enough of a risk of nuisance to satisfy the likelihood-
of-success requirement at this preliminary stage. See Van De
Sande v. Van De Sande, 431 F.3d 567, 570 (7th Cir. 2005) (“The
gravity of a risk involves not only the probability of harm,
but also the magnitude of the harm if the probability
materializes.”) (citing United States v. Carroll Towing Co., 159
F.2d 169, 173 (2d Cir. 1947)). In addition, the nature of the
threat – an ecological harm – suggests that a broader
perspective on the problem might be necessary. It is hard to
see 60 miles of separation between the carp invasion front
and the Great Lakes (and remember this was the estimated
distance more than two years ago) as a particularly safe
margin, even with functioning electric barriers to deter fish
and efforts to reduce propagule pressure (the volume of
invasive carp in the water downstream of the front). It is
especially chilling to recall that in just 40 years the fish have
migrated all the way from the lower Mississippi River to
within striking distance of the lakes and have come to
dominate the ecosystem in the process. Commercial
harvesting of carp in the Mississippi basin increased from
just over five tons to 55 tons in the three-year period from
1994 to 1997; there is evidence that by 1999 invasive carp
made up 97% of the Mississippi’s biomass; and as of 2007
commercial fishers were catching 12 tons of invasive carp
each day. These numbers are sobering even apart from the
hints that some of the fish may have made it into the CAWS
already.
No. 10-3891                                                    33

   In our view, the proper inference to draw from the
evidence is that invasive carp are knocking on the door to
the Great Lakes. We need not wait to see fish being pulled
from the mouth of the Chicago River every day before
concluding that a threat of a nuisance exists. It is enough
that the threat is substantial and that it may be increasing
with each day that passes. Unlike many nuisances that can
be eliminated after they are discovered, this one in all
likelihood cannot be. The fact that it would be impossible to
un-ring the bell in this case is another reason to be more
open to a conclusion that the threat is real. In our view, the
plaintiff states presented enough evidence to establish a
good or even substantial likelihood of success on the merits
of their public nuisance claim.


                               III
   Before moving on to the other preliminary injunction
factors, there are some particular questions about the APA
claim against the Corps that we must address. We turn
again to § 702 of the APA, which authorizes a suit by “[a]
person suffering legal wrong because of agency action, or
adversely affected or aggrieved by agency action within the
meaning of a relevant statute.” 5 U.S.C. § 702. A reviewing
court is required to “compel agency action unlawfully
withheld or unseasonably delayed,” 5 U.S.C. § 706(1), and to
“set aside agency action . . . found to be . . . arbitrary,
capricious, an abuse of discretion, or otherwise not in
accordance with law,” id. § 706(2)(A). The states do not ask
us to compel the Corps to take action, at least as far as §
706(1) is concerned. Norton v. Southern Utah Wilderness
Alliance, 542 U.S. 55, 64 (2004), explains that “a claim under
§ 706(1) can proceed only where a plaintiff asserts that an
agency failed to take a discrete agency action that it is required
to take”; the states have named no action that they think the
agency is required to take. We understand the states’
argument as a request to set aside agency action that they
regard as unlawful within the meaning of § 706(2)(A).
34                                                   No. 10-3891

   The obvious starting point is to identify the final Corps
action that the states assert has affected them. See 5 U.S.C.
§ 704; Lujan v. National Wildlife Fed’n, 497 U.S. 871, 882 (1990).
The states contend that five such actions fit the bill. They say
that the Corps’s (1) operation of the CAWS in a manner that
will let invasive carp into Lake Michigan, (2) reliance on
ineffective electric barriers, (3) use of locks in areas where
living and dead carp have been found, (4) denial of the
states’ requests for additional relief, and (5) implementation
of recommendations contained in the Corps’s third interim
report (which is part of the Efficacy Study we discussed in
connection with our analysis of displacement, supra) are all
final agency actions. The district court equivocated on the
issue, but it seems to have agreed with the states in the end.
  There is a good chance that most of the “actions” named
by the states are not “final agency actions” for purposes of
the APA. “Agency action” is defined as “the whole or a part
of an agency rule, order, license, sanction, relief or the
equivalent or denial thereof, or failure to act,” 5 U.S.C. §
551(13). The Supreme Court has explained that these
categories all “involve circumscribed, discrete agency
actions,” Norton, 542 U.S. at 62. Agency action is “final”
when it marks the consummation of the agency’s
decisionmaking process and determines legal rights or
obligations. Bennett v. Spear, 520 U.S. 154, 177-78 (1997); see
also Western Illinois Home Health Care, Inc. v. Herman, 150
F.3d 659, 662 (7th Cir. 1998) (citing Franklin v. Massachusetts,
505 U.S. 788 (1992), for the proposition that “[t]he core
question is whether the agency has completed its
decisionmaking process, and whether the result of that
process is one that will directly affect the parties”). Applying
these standards, we cannot see why any of the “actions” that
are numbered 1 through 4 on the states’ list of complaints
above should be considered final agency action. Most of the
four “actions” are not discrete at all; and those that might be
so classified do not represent the final outcome of any
decisionmaking process by the Corps. The Corps’s effort to
implement its third interim report – which recommended
No. 10-3891                                                   35

the installation of screens over two gates that control water
flow between the CAWS and Lake Michigan but which
otherwise called for normal operation of lake-facing locks –
is the only activity that may be suitable for an APA
challenge. We need not evaluate that claim in any detail,
however, because it is part of the states’ larger request for
relief based on the common law of public nuisance.
  Two types of plaintiffs are given a right of review in § 702:
those suffering a “legal wrong,” and those “adversely
affected or aggrieved by agency action within the meaning
of a relevant statute.” In their briefs in this court, the states
have not pointed to a single statute against which one might
judge the Corps’s behavior. (This is not surprising, given the
dearth of pertinent federal legislation that we discussed in
connection with displacement.) The Corps submits that this
means that the states have no APA claim; the states respond
their APA claim is “free-standing.” Neither answer is
satisfactory. We know that the states have not alleged that
the Corps’s actions failed to comply with some statutory
provision, and so they must instead be asserting that they
have suffered a “legal wrong” because of those actions. The
only legal wrong that comes to mind, however, is the
infliction of a common-law public nuisance. See Lujan, 497
U.S. at 883 (distinguishing between legal wrongs and the
failure of an agency to comply with a statutory provision);
Tennessee Electric Power Co. v. Tennessee Valley Authority, 306
U.S. 118, 137 (1939) (explaining that “legal wrong” includes
tortious invasions and interferences with property and
contractual rights). See generally Antonin Scalia, The
Doctrine of Standing as an Essential Element of the Separation of
Powers, 17 SUFFOLK U. L. REV. 881, 887-890 (1983) (discussing
the use of the term “legal wrong” in the APA and explaining
that it “could only mean a wrong already cognizable in the
courts”). The result is that the states’ APA claim against the
Corps sinks or swims (so to speak) with its public nuisance
theory. Because they are indistinguishable, we address only
the latter from this point on.
36                                                  No. 10-3891

                               IV
   To satisfy the second threshold requirement for
preliminary injunctive relief, the states must establish that
irreparable harm is likely without an injunction. Judge v.
Quinn, 612 F.3d 537, 557 (7th Cir. 2010). In the district court’s
view, this issue was the same as the question whether the
states had shown a likelihood of success on the merits of
their public nuisance claim. The states contend that it was
error to conflate these inquiries. They are right. In this case,
for example, the likelihood of success on the merits focuses
on the threat of a nuisance, while the irreparable harm is
concerned with the ability to correct that nuisance if it is
created. Not every nuisance will give rise to irreparable
harm. These two steps of the preliminary injunction analysis
thus play different roles. The likelihood of success on the
merits is an early measurement of the quality of the
underlying lawsuit, while the likelihood of irreparable harm
takes into account how urgent the need for equitable relief
really is. Typically, these lines of inquiry will have some
overlap, but they should not be treated as the same. With
that in mind, we realize that the same evidence will inform
both steps of the preliminary injunction analysis in this case.
As long as the distinctions we have just mentioned remain
clear, there is no harm in analyzing all of the evidence once
rather than twice. As a result, the states’ criticism of the
district court is largely academic and provides no reason to
reverse that court’s decision.
   Putting theory to one side, we have very little trouble
concluding that the environmental and economic harm that
the states have shown might come to pass would be
genuinely irreparable if it did occur. The district court
implied that this was the case when it discussed the
magnitude of the potential harm. Last year in Supreme
Court filings related to this litigation, the United States
explained in a memorandum that it agreed with Michigan
“that allowing a reproducing population of Asian carp to
establish itself in Lake Michigan likely would be an
irreparable injury.” Memorandum in Opposition of the
No. 10-3891                                                   37

United States, at 43, Original Nos. 1, 2, and 3,
http://w w w .suprem ecourt.gov/SpecM astRpt/U S_
Memorandum_in_Opposition.pdf; see also id. at 47 (calling
the harm “grave and irreparable”). All of the other parties
seem to agree with this view. (To the extent that the
defendants argue that there is no irreparable harm because
the carp cannot establish a breeding population in Lake
Michigan, they are avoiding the key question: what if the
fish did establish a successful breeding group?) This near-
unanimity on the question of irreparable injury makes sense.
“Environmental injury, by its nature, can seldom be
adequately remedied by money damages and is often
permanent or at least of long duration, i.e., irreparable.”
Amoco Prod., 480 U.S. at 545; Sierra Club v. Franklin County
Power of Illinois, LLC, 546 F.3d 918, 936 (7th Cir. 2008). Harms
like those the states allege here are irreparable because they
are difficult – if not impossible – to reverse. See Hollingsworth
v. Perry, 130 S. Ct. 705, 712 (2010) (per curiam).
  For preliminary relief to be granted, the irreparable harm
must also be likely. That is, there must be more than a mere
possibility that the harm will come to pass, Winter, 555 U.S.
at 21-23, but the alleged harm need not be occurring or be
certain to occur before a court may grant relief, United States
v. W.T. Grant Co., 345 U.S. 629, 633 (1953); United States v.
Oregon State Med. Soc’y, 343 U.S. 326, 333 (1952); Bath Indus.,
Inc. v. Blot, 427 F.2d 97, 111 (7th Cir. 1970). Commentators
describe the required level of certainty this way: “[A]
preliminary injunction will not be issued simply to prevent
the possibility of some remote future injury. A presently
existing actual threat must be shown. However, the injury
need not have been inflicted when application is made or be
certain to occur.” 11A C HARLES A LAN W RIGHT, ET AL.,
FEDERAL PRACTICE AND PROCEDURE § 2948.1, at 154-55 (2d ed.
1995). Because the district court analyzed likelihood of
success on the merits at the same time as it assessed the
danger of irreparable harm, all of the reservations we had
about the inferences drawn by the district court in the
former context apply with equal force here.
38                                                   No. 10-3891

   As we have already pointed out, no one knows whether
this irreparable harm will come to pass. The intense factual
dispute we are witnessing here about the rate at which
invasive carp are progressing makes evaluating its
likelihood even more tricky. In our view, the district court
required a level of proof too close to certainty when it
assessed the danger of invasive carp escaping into Lake
Michigan. Given the dire nature of the harm posed by the
carp and their close proximity to the CAWS, we again will
give the plaintiff states the benefit of the doubt. Just as they
produced enough evidence to establish a likelihood of
success on the merits warranting injunctive relief, so too
have they shown, to the degree necessary for preliminary
relief, that it is likely that irreparable harm will come to pass.
This sets the stage for the dispositive issue: how must the
harms the states have identified be balanced against those
that the defendants will suffer should an injunction be
granted?


                                V
  The balancing process to which we now turn is a classic
part of any preliminary injunction inquiry. See Winter, 555
U.S. at 24 (“A preliminary injunction is an extraordinary
remedy never awarded as of right. In each case, courts must
balance the competing claims of injury and must consider
the effect on each party of the granting or withholding of the
requested relief.”) (internal quotation marks and citations
omitted). How much of the danger forecast by the states
would be avoided by the particular injunction they have
asked for? And what harm would the injunction impose on
the defendants? Typically, after we balance these party-
specific equities, we evaluate whether the injunction would
advance or impede the public interest. See, e.g., Ferrell v. U.S.
Dep't of Hous. and Urban Dev., 186 F.3d 805, 811 (7th Cir.
1999). That additional analysis is not necessary in this case,
however, because the parties themselves, with the exception
of two intervenors, are governmental entities that represent
No. 10-3891                                                 39

the interests of the public.
   When it appears that preliminary relief may be
burdensome, the Supreme Court has instructed courts to be
careful as they balance the competing interests. Winter, 555
U.S. at 27; see also Kartman v. State Farm Mut. Auto. Ins. Co.,
634 F.3d 883, 892 (7th Cir. 2011). In light of the multifarious
ideas the states have for an injunction in this case, there can
be no doubt that caution must be our word of the day. Even
if a plaintiff’s suit appears to have merit, an injunction
should not necessarily issue if the harm to the defendant
would substantially outweigh the benefit to the plaintiff.
MacDonald v. Chicago Park Dist., 132 F.3d 355, 357 (7th Cir.
1997).
  In the end we conclude that a preliminary injunction
would cause significantly more harm that it would prevent.
We reach this result for two reasons, which we summarize
here before explaining the balance of harms in more detail.
First, there are a number of problems with various line items
in the plaintiffs’ proposed package of relief. Taken together,
these problems leave us doubting whether the proposed
injunction would reduce by a significant amount the risk
that invasive carp will gain a foothold in the Great Lakes
between now and the time that a full trial on the merits is
completed. It is clear, on the other side, that the requested
measures would impose substantial costs on the defendants
and the public interests they represent, as well as added
expenses for commerce, recreation, and tourism. Second, as
circumstances currently stand, there is a more fundamental
reason that the states’ requested injunction is unlikely to
prevent much harm and actually may impose costs. The
courts would not be acting alone. As we have explained,
there is a powerful array of expert federal and state actors
that are engaged in a monumental effort to stop invasive
carp from entering the Great Lakes. The last thing we need
is an injunction operating at cross-purposes with their
efforts or imposing needless transactional costs that divert
scarce resources from science to bureaucracy. Furthermore,
from an institutional perspective courts are comparatively
40                                                  No. 10-3891

ill situated to solve this type of problem. The balance of
harms favors the defendants and the public interests they
represent to such an extent that we conclude that the district
court’s decision to deny preliminary relief was not an abuse
of discretion.
                               A
                               1
  It is best to begin by trying to understand precisely what
preliminary relief the states would like. As the district court
noted, their request has evolved as the case has moved
forward. Indeed, their position has shifted even between
their opening brief in this court and oral argument. The
moving nature of the target complicates our job of
evaluating the propriety of injunctive relief. Moreover, their
request has been phrased at a high level of generality. They
have given us the broad strokes of additional steps they
would like us to order the defendants to take, but they have
not furnished many details about how this relief would be
implemented, on what schedule, at what cost, and on whose
nickel. From time to time the states urge that the injunctive
measures should be “consistent with public health and
safety,” but they do not say what precisely that means. This
vagueness is unhelpful; it stands as an obstacle to the entry
of an injunction that will satisfy Federal Rule of Civil
Procedure 65(d). See PMC, Inc. v. Sherwin-Williams Co., 151
F.3d 610, 619-20 (7th Cir. 1998); see also Patriot Homes, Inc. v.
Forest River Hous., Inc., 512 F.3d 412, 414-15 (7th Cir. 2008).
When a plaintiff seeks relief of the type the states ask for
here, we have required a more specific plan about the
measures to be taken and the costs of implementing those
measures. See Jordan v. Wolke, 593 F.2d 772, 774-75 (7th Cir.
1978).
  At this time, it is our understanding that the states believe
that they are entitled to a preliminary injunction that would
require the defendants to take these five steps:
  a. Closing the Locks. Close and stop operating the locks at
No. 10-3891                                                 41

  the Chicago River Controlling Works (the Controlling
  Works) and the O’Brien Lock and Dam (O’Brien), which
  sit at two of the five points of contact between the CAWS
  and Lake Michigan;
  b. Screens over Sluice Gates. Install nine additional screens
  over sluice gates that are used to control water flow
  between the CAWS and the lake at the Controlling Works,
  O’Brien, and the Wilmette Pumping Station, a third
  contact point with Lake Michigan;
  c. Block Nets in the Rivers. Place block nets to stop fish in
  the Little Calumet River, which connects the CAWS to the
  lake at the Burns Small Boat Harbor in Indiana, and if
  necessary in the Grand Calumet River, which runs
  between the CAWS and the Indiana Harbor and Canal
  (Burns Harbor and Indiana Harbor are last of the five
  contact points between the CAWS and Lake Michigan);
  d. Rotenone Poisoning. Use rotenone to poison fish in the
  CAWS, especially in areas north of O’Brien.
  e. Accelerating GLMRIS. Finish the part of the Great Lakes
  and Mississippi River Interbasin Study that relates to the
  CAWS, which Congress called for in the Water Resources
  Development Act of 2007, within 18 months.
The states have made two additional requests that do not
require discussion. They say that the defendants should use
the best methods to stop, capture, and kill carp that are
present in the CAWS. We see this as a more general
statement of the specific measures we have just outlined. In
addition, the states want the defendants to continue using
monitoring techniques, including eDNA testing, to search
for invasive carp. But the Corps and the other agencies
working on this problem are continuing eDNA monitoring
efforts. In July 2011, for example, three rounds of positive
eDNA testing results led to a four-day hunt for invasive carp
(none was found). This request asks for steps already being
taken, and so we will not discuss it further.
                              2
42                                                No. 10-3891

   Before we discuss the harm and benefit of the preliminary
relief the states request, we must point out an error in the
states’ view of how the harms should be weighed. The states
say that any harm the defendants might suffer because of
the injunction pales “in comparison to the grave and truly
irreparable harm that will occur if Asian carp establish a
breeding population in the Great Lakes.” But that is not the
correct measure of the harm avoided by the states’ proposed
injunction. The states assume, without providing much
explanation, that preliminary relief would stop invasive carp
from ever reaching the Great Lakes. While that may be the
effect that a perfectly designed permanent injunction would
have, it is not an accurate measure of the harm that would
be avoided by the states’ proposed preliminary injunction.
At this early point, the question is to what extent would the
proposed measures decrease the risk of invasive carp
establishing themselves in the Great Lakes between now and
when the litigation concludes? Stepping back from the
subject matter of this litigation, we note that in addition to
the CAWS, the Corps has identified a total of 18 places in
Minnesota, Wisconsin, Indiana, Ohio, and New York where
invasive carp could move from the Mississippi basin into the
Great Lakes. These pathways outside of the CAWS
necessarily reduce the likelihood that the states’ preliminary
injunction will prevent carp from establishing themselves in
the Great Lakes, because the states’ proposed measures say
nothing about these alternate routes. Even focusing
exclusively on the CAWS, the states overlook similar
limitations inherent in the steps they are proposing –
limitations that would reduce the effectiveness of
preliminary relief, as we now explain.
  a. Closing the Locks. If the locks at the CRCW and O’Brien
are closed, the states concede that the closure need not be
permanent or unqualified; instead, they say, the locks may
be opened if closure would put public health or safety at
risk. We are not sure how that would work. The City of
Chicago says that police and fire services use the locks
routinely, as do Coast Guard boats. At one point, the states
No. 10-3891                                                 43

agreed that passage for emergency boats through the locks
was needed for public safety. That sounds reasonable to us.
Now, however, their injunction would allow the defendants
to open the locks only when the District needs to release
water from the CAWS into the lake to control flooding
(during so-called “reversal” operations). The states’
proposed injunction is made more effective by keeping the
locks closed to all boat traffic, but in so doing, it increases
the cost to emergency services. Even in its current iteration,
the efficacy of the states’ plan for closing the locks is
compromised because any flooding that would require the
defendants to conduct reversal operations decreases the
chances that the carp will be stopped – when the locks are
open, water pours out of the CAWS and into Lake Michigan.
(This happened most recently on July 24, 2011, after nearly
seven inches of rain fell in only two hours, see Michelle
Gallardo, 2 Locks Opened During Record Rainfall, Chicago
Tribune, July 25, 2011, http://abclocal.go.com/wls/story?
section=news/ local&id=8270514. It also happened exactly
one year before, on July 24, 2010.) A related complication
concerns how effectively the locks stop fish even when they
are closed. By most accounts, a watertight closure would
require bulkheads to be installed on the locks. Without
bulkheads, fish might slip through small openings. The
states have been less than explicit about whether their ideal
injunction would require bulkheads, but if it would, then all
the risks of flooding come right back into the equation.
Bulkheads take time to install and remove, which means
that it would be very difficult to respond quickly to floods.
In short, this aspect of the states’ requested relief puts them
into a bind: the risk of carp migration is reduced the most by
closing the locks permanently with bulkheads; but that
measure, as the states recognize, would dramatically
escalate the costs imposed by flooding. While keeping the
locks closed more often no doubt reduces the risk of fish
migrating into Lake Michigan, it does not bring it down to
zero. And this unquantified reduction in risk comes with an
increased immediate burden on public health and safety
measures.
44                                                 No. 10-3891

  b. Screens over Sluice Gates. The states encounter similar
problems with their request that the defendants screen off
nine additional sluice gates. The District operates these huge
gates, which open and close to adjust the rate of water flow,
as part of its diversion effort – the process of drawing water
out of Lake Michigan and into the CAWS to maintain
navigability and water quality. In addition, when heavy
rains occur, sluice gates (like the locks) are opened to let
water from the CAWS into the lake. There are eight sluice
gates at the Controlling Works, four at O’Brien, and one in
Wilmette. To prevent the migration of adult carp, the
District already has installed four screens over sluice gates:
two at the Controlling Works and two at O’Brien. The
District uses the four screened-off gates for diversion; the
other nine remain closed except during flooding.
   Initially, the states wanted to force the defendants to close
all of the gates, except when public health or safety might be
harmed. They have revised that request so that now they ask
for screens over the nine remaining sluice gates at these
sites. This request would mitigate the risk of carp migration
only (at best) during floods, for at other times the gates,
unlike the locks, are closed anyway. Further reducing the
effectiveness of this measure is the fact that in some flooding
incidents where additional sluice gates must be opened, the
locks must be opened as well. Screens over additional sluice
gates would not do much good if fish could swim through
open locks. Finally, all available evidence suggests that it
will take a long time for the District to acquire additional
property, to research feasible options for a system of screens
that will not become clogged with debris during flooding,
and to build those screens. This means that this portion of
the states’ preliminary injunction might not even be in place
before the full trial on the merits has concluded. For all of
these reasons, we think that installing screens over sluice
gates will have at most a tiny effect on the odds of invasive
carp making it to Lake Michigan.
  c. Block Nets in the Rivers. The prospect of placing block
nets in the Little Calumet and Grand Calumet Rivers strikes
No. 10-3891                                                                     45

us as potentially the most effective element of the proposed
relief. At the time of oral argument, the states asked that the
Corps place block nets only in the Little Calumet River; at
that point, a cofferdam in the Grand Calumet River
prevented fish migration and alleviated the need for nets
there. We will assume that were this dam removed, the
states would ask the Corps to place nets in the Grand
Calumet River as well. The Corps, however, has said that it
is already looking at the possibility of installing nets in both
waterways, but that it is concerned that flooding will
increase as debris becomes caught in the nets. The states
respond that block nets could be cut free and replaced with
new nets if risks of flooding materialized. All of the parties
are vague about the possibilities and implications of this
plan. At this stage, it is enough to say that this step seems
more promising than others when it comes to mitigating the
risk that fish will appear in Lake Michigan. We take the
Corps at its word that this option is under serious
consideration and would be implemented if and when a
feasible plan can be developed.
   d. Rotenone Poisoning. In contrast to the block net idea, the
suggestion that the Corps use rotenone to poison fish in the
CAWS seems untenable to us. Rotenone is a chemical that
acts as a piscicide when it is released in a body of water.
Though humans would not digest much of it if it were
ingested, rotenone enters the bloodstream of a fish through
the gills, causing death quickly. Rotenone dumped into a
river kills the vast majority of fish living there; when dead,
they usually float to the surface. The poison generally is less
dangerous to other animals, but it is toxic and its toxicity
varies depending on the species. See generally Cornell
University, Resource Guide for Organic Insect and Disease
Management, Material Fact Sheets - Rotenone,
h tt p ://w e b .p p p m b .c a l s .c o r n e l l .e d u / r e s o u r c e gu id e/
mfs/11rotenone.php. It is unclear just how the states’
proposal for rotenone use differs from what the Corps is
already doing in the CAWS. We know that the states would
like poison to be applied near O’Brien, but there is no
46                                                No. 10-3891

indication how often or where else it might be used. In May
2010, the Corps and other agencies used the poison to search
for fish in a two-mile stretch of the Little Calumet River.
Dozens of tons of fish were killed, and no specimens of
invasive carp were found. While poisoning may be an
effective way to search for elusive carp in some
circumstances, the record does not explain why ordering the
Corps to poison the CAWS on a regular basis would be a
sound step toward reducing the risk that invasive carp will
migrate into the Great Lakes.
  e. Accelerating GLMRIS. That brings us to the aspect of the
proposed injunction that would require the Corps to
accelerate its long-term study of ways in which it might
permanently prevent the migration of invasive species
(including, but not limited to, the carp) between the Great
Lakes and the Mississippi basins. The states raise a side
issue here, saying that the district court erred when it denied
their request to expedite GLMRIS because it failed to make
the findings required by Federal Rule of Civil Procedure
52(a)(2). The argument is frivolous. The district court
explained its reasons for denying all of the relief that the
states sought. The court had – and will continue to have as
the case moves forward – the power to grant or deny
equitable measures either in whole or in part. It did not need
to discuss every facet of the relief requested.
  According to the Corps, GLMRIS examines every potential
pathway between the two watersheds and proposes
solutions to stop migration through each one. Examination
of the CAWS, which the Corps intends to finish by 2015, is
just one portion of the study. The Corps adds that it has the
power to implement solutions that are devised as the study
progresses. The states would like the court to order the
Corps to finish the CAWS portion of GLMRIS within 18
months. They are not the only ones who have criticized the
study for taking too long; the City of Chicago and others
have as well. See, e.g., Dan Egan, Chicago Urges Army Corps
to Report on Carp Sooner, Milwaukee Journal Sentinel, Apr.
10,     2011,       http://www.jsonline.com/
No. 10-3891                                                 47

news/wisconsin/119547049.html. It may well be that faster
action is appropriate if possible; and, as the Corps conceded
during oral argument, it may be necessary for the Corps to
implement measures devised through GLMRIS on a rolling
basis. But we do not see how a preliminary injunction that
would essentially ask the Corps to study harder and think
faster would reduce the odds that invasive carp will
establish themselves in the short term.
  When we take all five aspects of the states’ proposed
injunction together, we can say only that there is some
evidence that the relief sought would reduce by an
undefined amount the risk of carp establishing a breeding
population in the Great Lakes. It is equally apparent,
however, that the steps the states have proposed offer no
assurance that they will block the carp over the short run or,
over the long run, that they will save the Great Lakes
ecosystem and the $7 billion industry that depends on that
ecosystem. We must therefore turn to the other side of the
equation: the harm that the proposed steps would inflict on
the opponents of preliminary relief.
                              3
  The states have adopted a rather insouciant attitude about
the potential harm that their proposal might inflict. “[T]he
federal government has made it clear that it is willing to
spend significant resources to reduce this threat,” the states
write, “so the cost of a few bulkheads should not prove a
serious impediment to protecting the Great Lakes.” This
tone continues throughout their briefs, with remarks like,
“While the Corps asserts that the Coast Guard doesn’t have
the funds to [dock additional ships on both sides of locks
that would be closed by the injunction], this is just a matter
of money.” Of course this dispute is in part a matter of
money; but scoffing at the defendants’ concerns about the
costs of relief does not aid our assessment of the expense of
the relief that the states want. It should go without saying in
these straitened times that the federal and local governments
do not have bottomless coffers. Indeed, 19 members of the
48                                                  No. 10-3891

plaintiff states’ delegations to Congress recently voted
against raising the federal borrowing limit. Nor do we
understand why the states take this view when they
apparently feel no obligation to contribute to the costs of
averting this crisis. When we inquired at oral argument how
the costs of the proposed injunction should be apportioned
among the parties, the states informed us that their citizens
would contribute to the costs by paying federal income
taxes. This is not very helpful. Indeed, one might wonder
why the federal government and the State of Illinois should
be saddled with the entire cost of an injunction that is aimed
at a problem that has been developing for four decades in a
watershed that touches roughly half of the states in the
Union.
  To make matters worse, both sides throw around large
numbers to make the case that the balance of harms favors
their position. We have already explained why the proposed
injunction is quite unlikely to prevent the states’ forecasted
$7 billion in harm. But the defendants invent similarly
extreme costs. We are told repeatedly that almost $2 billion
in cargo moves through locks in the CAWS each year. This,
however, is not the cost that an injunction would impose on
commercial shipping. If the locks were closed, cargo would
have to be loaded from ships onto ground transportation at
some point along the journey. Estimates of the cost of
off-loading range from about $70 million per year (from the
plaintiffs’ perspective) to $150 million (according to the
Corps). The intervening defendant Coalition to Save Our
Waterways, which represents various business interests,
tells us that closing the locks would cost $4.7 billion. We find
no support in the record for that astronomical estimate. The
dollar value of the harm to either side is of course difficult to
calculate, but we need not settle on a precise number to
resolve this appeal.
  If the requested preliminary injunction were to issue, we
can be sure that it would impose significant costs. First, we
would have the expenses of implementing all of the
measures that the states have recommended. In addition,
No. 10-3891                                                 49

funds that the defendants spend complying with the
injunction likely would be diverted from other agency
efforts to curb invasive carp. If we required the Corps to
complete its long-term study within 18 months, the Corps
suggests that it would not have time study the problem
comprehensively and that the study might not adequately
support any proposed solutions. The prospect of closing the
locks permanently, installing screens on sluice gates, and
placing block nets in the CAWS increases the risk of
flooding, which (to the extent that it occurs) would impose
costs throughout the region. The states say that there are
ways to avoid those costs. The locks, for example, could be
opened at the District’s discretion during flooding. But, as
we have explained, this would be possible only if the states
agreed that bulkheads were not necessary. (The states argue
that bulkheads could be removed by a barge and crane to
permit for flood relief. Even if that were possible, stationing
barges at both locks would cost thousands of dollars per
day.) Screens installed over sluice gates used during
flooding could become clogged, and the states’ suggestion
that raking systems be installed to alleviate this concern is
both untested and would required significant additional
expenditures. Meanwhile, closing the locks to boat traffic
would have a tremendous impact. Police and fire services on
which the City of Chicago relies would not be able to move
from the Chicago River and other points in the CAWS to
Lake Michigan, which means that the city would have to
establish redundant emergency response fleets on either side
of the locks. The same goes for Coast Guard operations
around the CAWS. Recreational and tourist vessels would
be stopped. And last but certainly not least, closed locks
would mean that all commercial shipping in the area
between the Great Lakes and the Mississippi would have to
find alternative routes.
  We can stop there. This overview demonstrates that the
preliminary injunction the states have requested would
impose substantial costs, yet given the current state of the
record, we are not convinced that the preliminary injunction
50                                                 No. 10-3891

would assure much of a reduction in the risk of the invasive
carp establishing themselves in Lake Michigan in the near
future. That the balance of harms at this stage of the
litigation favors the defendants might be enough by itself to
support a conclusion that preliminary relief is not
warranted, even though we have concluded that the states
have demonstrated a likelihood of success on the merits and
a threat of irreparable harm. See Hoosier Energy Rural Elec.
Co-op v. John Hancock Life Ins. Co., 582 F.3d 721, 725 (7th Cir.
2009) (describing the relation between the harm prevented
by the plaintiff’s proposed injunction and the strength of a
plaintiff’s claim for preliminary relief). Even if one were to
conclude that the harms are in equipoise, however, there is
a final reason why preliminary injunctive relief is not
warranted. As things now stand, the case for judicial
intervention is refuted by the fact that the competent federal
and state actors are actively pursuing an array of efforts to
solve the problem of invasive carp.
                               B
                               1
   While American Electric Power is a case about congressional
displacement of federal common law, the Supreme Court
took the opportunity to touch generally on the relative
competence of courts and expert agencies when it comes to
solving complex environmental problems. “It is altogether
fitting that Congress designated an expert agency, here,
EPA, as best suited to serve as primary regulator of
greenhouse gas emissions,” the Court wrote, explaining
further:
  The expert agency is surely better equipped to do the job
  than individual district judges issuing ad hoc,
  case-by-case injunctions. Federal judges lack the
  scientific, economic, and technological resources an
  agency can utilize in coping with issues of this order.
  Judges may not commission scientific studies or
  convene groups of experts for advice, or issue rules
  under notice-and-comment procedures inviting input by
No. 10-3891                                                    51

  any interested person, or seek the counsel of regulators
  in the States where the defendants are located. Rather,
  judges are confined by a record comprising the evidence
  the parties present. Moreover, federal district judges,
  sitting as sole adjudicators, lack authority to render
  precedential decisions binding other judges, even
  members of the same court.
American Electric Power, 131 S. Ct. 2539-40 (internal citation
omitted). This limitation of the judiciary is a familiar feature
of American law. See, e.g., Negusie v. Holder, 129 S. Ct. 1159,
1171 (2009) (Stevens, J., concurring in part and dissenting in
part); Kelo v. City of New London, 545 U.S. 469, 487-88 (2005);
Lingle v. Chevron U.S.A., Inc., 544 U.S. 528, 544-45 (2005);
Chevron, U.S.A., Inc. v. Natural Res. Def. Council, Inc., 467 U.S.
837, 865-66 (1984); Tennessee Valley Authority v. Hill, 437 U.S.
153, 194-95 (1978).
  Our sister circuits have explored the impact of this
inherent limitation of the judicial role in cases comparable to
ours. The Second Circuit has written that “[c]ourts
traditionally have been reluctant to enjoin as a public
nuisance activities which have been considered and
specifically authorized by the government.” New England
Legal Found. v. Costle, 666 F.2d 30, 33 (2d Cir. 1981). In the
same vein, the Fourth Circuit recently reversed a lower
court’s decision to enter an injunction that would have
required the TVA to implement new emissions controls.
North Carolina, ex rel. Cooper, 615 F.3d 291. The district court
in that case entered an injunction after North Carolina sued
the TVA for air pollution based on a state common-law
public nuisance theory. The court of appeals concluded that
granting “the injunction would encourage courts to use
vague public nuisance standards to scuttle the nation’s
carefully created system for accommodating the need for
energy production and the need for clear air.” Id. at 296.
Though the case involved a more robust regulatory scheme
than the one that has been cobbled together for the invasive
carp, the court’s discussion is instructive insofar as it relates
to the problems created when courts attempt to stop a
52                                                  No. 10-3891

nuisance at the same time that agencies are working to solve
the problem. An approach that would allow the federal
court and the EPA simultaneously to regulate a single
emissions problem, said the Fourth Circuit, would result in
multiple and perhaps contradictory decrees emanating from
different branches of government and confusion about what
standards should govern air pollution. Id. at 301-04. In
addition, judicial action in the face of strong agency
measures “would reorder the respective functions of courts
and agencies.” Id. at 304. Environmental problems require
the balancing of many complicated interests, and agencies
are better suited to weigh competing proposals and select
among solutions. Id. at 305 (“[W]e doubt seriously that . . . a
judge holding a twelve-day bench trial could evaluate more
than a mere fraction of the information that regulatory
bodies can consider.”).
   None of this means that courts can no longer craft
remedies designed to abate a public nuisance. In light of the
general approach the Supreme Court took in American
Electric Power, however, it does mean that the court should
not blind itself to other remedies that are available under the
law or to other measures that are actively being pursued to
solve the problem. Even if legal displacement like that found
in American Electric Power does not exist, the practical effect
of agency actions might add up to displace as a matter of
fact any role that equity might otherwise play. Efforts of
other branches of government might be so complete that
additional action ordered by a court would risk
undermining agency efforts to abate the nuisance. How
much the equitable power of the court has been limited by
agency action will be a factual question that turns on the
quality and quantity of the agency’s (or, as here, agencies’)
efforts. This kind of institutional consideration of the court’s
relative ability to craft meaningful relief fits naturally in the
balance-of-harms analysis. For if an injunction might
hamper agency efforts or can improve upon them only
slightly, that is all the more reason to conclude that the
equities tilt in favor of the defendant.
No. 10-3891                                                     53

                                2
  The record in this case leaves no doubt that federal and
state agencies, executive officials, and working groups have
mounted a tremendous effort to halt the migration of
invasive carp. As we have already mentioned, the Aquatic
Nuisance Prevention and Control Act of 1990 created the
Aquatic Nuisance Species Task Force, which includes among
other agencies the National Oceanic and Atmospheric
Administration, the U.S. Fish and Wildlife Service, the U.S.
Geological Survey, and the EPA. This task force coordinates
invasive species issues generally across the country. In
addition, during the fall of 2009, 21 federal, state, and local
agencies and other entities combined forces to form the
Asian Carp Regional Coordinating Committee (the ACRCC),
which is designed (as the name suggests) to track and to
stop the migration of invasive carp. See generally Asian
Carp Control, http://www.asiancarp.org/. The ACRCC
counts as members those agencies that comprise the task
force, the Corps and the District, the Coast Guard, the U.S.
Department of Transportation, the White House Council on
Environmental Quality, the Great Lakes Fishery
Commission, the City of Chicago, and the state departments
of natural resources of all of the plaintiff states, plus Illinois,
Indiana, and New York.
  In order to stop the invasive carp, the ACRCC has
developed what it calls the “Asian Carp Control Strategy
Framework,” which is now in its third edition. The most
recent document lists over 40 collaborative projects that the
working group has designed to deal with invasive carp;
many of these initiatives are underway or have been
completed already. As the ACRCC describes it, the projects
fall into eight categories:
  (1) targeted monitoring assessment activities above and
  below the electric barrier system, including enhanced
  monitoring above and below the barriers, electrofishing,
  and rapid response teams;
  (2) commercial harvesting and removal actions below
54                                                No. 10-3891

 the electric barriers (which involves fishing and removal
 of fish in the Lockport area, where the CAWS connects
 to the Des Plaines River; creating new markets for the
 fish; and investigating certification requirements for
 invasive carp to be sold commercially);
 (3) electric barrier actions and waterway separation
 measures (consisting of the construction of barriers
 between various waterways so that fish cannot move
 from one to the other during flooding; expedited
 construction of the now-completed third electric barrier;
 fish tagging to test the effectiveness of the barriers; and
 separation of various watersheds that pose risks);
 (4) myriad studies on how best to separate the
 watersheds; the effectiveness of various measures; and
 risk modeling;
 (5) research and technology development (including
 investigation of how fish move around the CAWS; food
 sources for invasive carp in the lakes and how those
 sources might be eliminated; the use of seismic
 technology to divert or kill invasive carp; attraction and
 repulsion pheromones of invasive carp; creation of toxin
 screens to kill fish; study of the weaknesses of carp to
 different toxins; physical barriers; reducing carp egg
 viability; and new detection methods, among other
 things);
 (6) eDNA analysis and refinement (which involves
 monitoring and sampling for eDNA in the CAWS and
 increasing the effectiveness of eDNA testing);
 (7) enforcement activities designed to prevent people
 from transferring carp between bodies of water; and
 (8) work on funding, including the development of
 methods to pay for measures among the contributing
 groups.
In addition, the ACRCC has established three working
groups: monitoring and rapid response; invasion control;
No. 10-3891                                                   55

and communication and outreach.
   What we have described already reflects a substantial
effort, but there is more. The Corps has been fulfilling the
marching orders that it has received from Congress. In
addition to the electric barriers and GLMRIS, which we have
discussed in detail, we have mentioned the Corps’s study of
the effectiveness of its three electric barriers for stopping the
movement of invasive carp through the CAWS. The final
version of the Efficacy Study is due later this year, but there
already have been four interim reports (numbered in typical
bureaucratic fashion as Interim I, II, III, and IIIA), and the
Corps has implemented measures pursuant to some of these
reports. Interim I identified an area where the Des Plaines
River and the Chicago Sanitary and Ship Canal are so close
together that carp could wash between them during floods.
(The plaintiffs had argued in their complaint that this area
represented a huge problem.) The Corps has since built a
fence to stop migration between these waterways, and that
fence has already proven effective. Meanwhile, Interim II,
which is not yet completed, will set operational parameters
for the three electric barriers so that they can most effectively
deter the movement of invasive species. The Corps says that
even though this study is not finished, it now operates the
barriers at the maximum safe strength. In connection with its
Interim III report, the Corps consulted a panel of experts
about a number of potential changes to its operation of the
CAWS. The report concluded that additional screens should
be installed on sluice gates, and the District responded by
adding screens to two gates at O’Brien, which supplemented
the two it had installed months earlier at the Controlling
Works. In addition, Interim III recommended that the
District cease using the sluice gate at Wilmette for diversion,
and it hypothesized that the District might be able to create
“atoxic zones” in the CAWS that would be so toxic that no
fish would ever be able to swim through them. Finally, the
Corps in Interim IIIA recommended the construction of an
acoustic, air-bubble, and strobe-light curtain (more or less a
disco screen), which would be designed to frighten fish back
56                                                No. 10-3891

toward the Mississippi. The disco screen has not been
started, but the Corps represented to us at oral argument
that it intends to undertake the project at some location
downstream of the existing electric barriers.
  In addition to the measures outlined in the interim efficacy
reports, the agencies continue to rely on traditional methods
to monitor and kill invasive carp, including tracking,
netting, electrofishing, and rotenone poisoning; and, as we
have discussed, they have also continued eDNA testing
throughout the CAWS. Where eDNA reveals a potential
threat, the agencies have responded with days-long hunts
for invasive carp. Continual fishing south of the CAWS
reduces the propagule pressure that would otherwise push
carp closer to Lake Michigan. Finally, the Obama
Administration has named an “Asian carp czar,” who is
charged with leading the administration’s effort to stop
invasive carp. Recently, the administration announced plans
to install a high-intensity water cannon that would deter fish
by firing huge, underwater blasts of water across Chicago
Ship and Sanity Canal.
  It is our understanding that the defendants and the
agencies we have just discussed are actively pursuing the
measures that we have just described. In addition, where the
defendants have represented that future steps will be taken
– whether a disco screen, the water gun, operating the
electric barriers at optimal settings, considering the
possibility of block nets in the CAWS, completing and
implementing GLMRIS in phases, continuing to monitor
aggressively with traditional and eDNA techniques, or any
of the other actions we have highlighted – we have no
reason at this point to assume that this work will not be
done. Whatever happens, the plaintiff states will continue to
have a seat at the table as these and future plans are made
and implemented. We conclude that on this record, there is
nothing that any preliminary injunction from the court could
add that would protect the Great Lakes from invasive carp
while this suit is being adjudicated any better than the
elaborate measures we have just described. This tips the
No. 10-3891                                                57

balance of harms decisively in favor of the defendants.


                             VI
   We take very seriously the threat posed by the invasive
species of carp that have come to dominate parts of the
Mississippi River basin and now stand at the border of one
of the most precious freshwater ecosystems in the world.
Any threat to the irreplaceable natural resources on which
we all depend demands the most diligent attention of
government. As the case proceeds, the district judge should
bear in mind that the risk of harm here depends upon both
the probability of the harm and the magnitude of the
problem that would result. In the end, however, the question
whether the federal courts can offer meaningful equitable
relief – either preliminary or permanent – to help abate a
public nuisance in the face of agency action is factual in
nature . It depends on the actual measures that the agencies
have implemented already and those that they have
committed to put in place going forward. Our ruling today
is tied to our understanding of the current state of play. We
recognize that the facts on the ground (or in the water) could
change. The agencies currently working hard to solve the
carp problem might find themselves unable to continue, for
budgetary reasons, because of policy changes in
Washington, D.C., or for some other reason. If that happens,
it is possible that the balance of equities would shift.
Similarly, new evidence might come to light which would
require more drastic action, up to and including closing
locks on Lake Michigan for a period of time. If either
situation comes to pass, then the district court would have
the authority to revisit the question whether an exercise of
its equitable powers is warranted, taking into account the
principles we have discussed in this opinion. As things
stand now, however, preliminary relief is not appropriate.
The district court’s judgment is AFFIRMED.
