                   FOR PUBLICATION
  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT

UNITED STATES OF AMERICA, on its          
own behalf and as trustee on
behalf of the Lummi Nation,
                    Plaintiff-Appellee,
                   v.
KEITH E. MILNER,
                            Defendant,          No. 05-35802
                  and                            D.C. No.
                                              CV-01-00809-RBL
BRENT C. NICHOLSON; MARY K.
NICHOLSON,
             Defendants-Appellants,
                   v.
LUMMI NATION,
       Plaintiff-intervener-Appellee.
                                          




                              14457
14458             UNITED STATES v. NICHOLSON



UNITED STATES OF AMERICA, on its        
own behalf and as trustee on
behalf of the Lummi Nation,
                  Plaintiff-Appellee,
                 v.
KEITH E. MILNER,
              Defendant-Appellant,
SHIRLEY A. MILNER; MARY D.                    No. 05-36126

                                        
SHARP; IAN C. BENNETT; MARCIA                   D.C. No.
A. BOYD,                                    CV-01-00809-RBL
             Defendants-Appellants,
                                               OPINION
                and
BRENT C. NICHOLSON; MARY K.
NICHOLSON,
                         Defendants,
                 v.
LUMMI NATION,
                Plaintiff-intervener.
                                        
        Appeal from the United States District Court
          for the Western District of Washington
        Ronald B. Leighton, District Judge, Presiding

                  Argued March 13, 2008
                 Submitted October 9, 2009
                    Seattle, Washington

                    Filed October 9, 2009
                     UNITED STATES v. NICHOLSON                      14459
        Before: Betty B. Fletcher, Richard A. Paez and
            Richard C. Tallman,* Circuit Judges.

                   Opinion by Judge B. Fletcher




  *Judge Tallman was drawn to replace Judge William W. Schwarzer,
Senior United States District Judge for the Northern District of California,
and has read the briefs, reviewed the record, and listened to a recording
of oral arguments.
                 UNITED STATES v. NICHOLSON           14463




                        COUNSEL

Richard M. Stephens, Groen Stephens & Klinge LLP, Belle-
vue, Washington, for the defendants-appellants.

Brian Kipnis, Office of the United States Attorney, Seattle,
Washington, for the plaintiff-appellee.

Harry L. Johnsen, Raas, Johnsen & Stuen, P.S., Bellingham,
Washington, for the plaintiff-intervenor-appellee.

Edgar B. Washburn, Morrison & Foerster LLP, San Fran-
cisco, California, for Amicus Building Industry Legal
Defense Foundation.

John Briscoe, Briscoe Ivester & Bazel LLP, San Francisco,
California, for Amicus Bay Planning Coalition.


                        OPINION

B. FLETCHER, Circuit Judge:

   In this appeal we decide whether a group of waterfront
homeowners are liable for common law trespass and viola-
tions of the Rivers and Harbors Appropriation Act of 1899
14464                UNITED STATES v. NICHOLSON
(RHA), 33 U.S.C. § 403, and the Clean Water Act (CWA), 33
U.S.C. § 1311, because the ambulatory tideland property
boundary has come to intersect shore defense structures the
homeowners have erected. In a series of summary judgment
rulings and after a bench trial, the district court found against
the homeowners and ordered them to remove violating struc-
tures and to pay a $1500 civil penalty. We affirm in part and
reverse in part.

                                     I.

   In 1855, the United States executed the Treaty of Point
Elliott with several Indian tribes, thereby acquiring a vast
swath of what is now western Washington.1 Treaty Between
the United States and the Dwámish, Suquámish, and Other
Allied and Subordinate Tribes of Indians in Washington Ter-
ritory, Jan. 22, 1855, 12 Stat. 927 (1859) (the “Treaty of Point
Elliott” or the “Treaty”). Under the terms of the Treaty, the
tribes were relegated to certain reserved areas, including “the
island called Chah-choo-sen,” on which the Lummi Indian
Reservation was created for the plaintiff-intervenor, the
Lummi Nation. Id. at 928. Although the Lummi initially occu-
pied only the island, by an executive order, President Grant in
1873 expanded the reservation to encompass portions of the
mainland, including Sandy Point, a sandy spit, all in what is
now Whatcom County, Washington. Exec. Order (Nov. 22,
1873), reprinted in 1 Charles J. Kappler, Indian Affairs: Laws
and Treaties 917 (1904), available at http://digital.library.
okstate.edu/kappler/Vol1/ Images/v1p0917.jpg. Importantly,
the order extended the reservation boundaries to “the low-
water mark on the shore of the Gulf of Georgia.”2 Id. In other
  1
     The Treaty of Point Elliott is one of a series of treaties negotiated by
Territorial Governor Isaac Stevens with various Pacific Northwest Indian
tribes in the mid-1800s. See generally Washington v. Wash. State Com-
mercial Passenger Fishing Vessel Ass’n, 443 U.S. 658, 661-62 (1979);
Nez Perce Tribe v. Idaho Power Co., 847 F. Supp. 791, 805-06 (D. Idaho
1994).
   2
     The “Gulf of Georgia” is now known as the Strait of Georgia.
                  UNITED STATES v. NICHOLSON              14465
words, President Grant explicitly expanded the reservation to
include the tidelands of the relevant area. United States v.
Stotts, 49 F.2d 619, 619, 621 (W.D. Wash. 1930).

   As allowed under President Grant’s executive order, the
uplands were divided into lots and patented by members of
the tribe. Defendants-appellants Keith and Shirley Milner (the
“Milners”), Mary Sharp, Brent and Mary Nicholson (the
“Nicholsons”), and Ian Bennett and Marcia Boyd
(“Bennett/Boyd”) (collectively, the “Homeowners”) are the
successors in interest to some of the parcels derived from
these original patents. The Homeowners’ parcels all adjoin
tidelands on the Strait of Georgia.

   Unlike the Homeowners’ properties, the tidelands within
the Lummi Reservation have otherwise never been alienated.
Plaintiff-appellee the United States claims that it continuously
has held the tidelands in trust for the Lummi Nation, pursuant
to President Grant’s executive order. Not surprisingly, then, it
is at the boundary between the tidelands and the uplands that
the present dispute finds its locus.

   Although each property is slightly different, the Homeown-
ers or their predecessors erected various “shore defense struc-
tures” to limit erosion and storm damage to their properties.
The structures generally include “rip rap,” large boulders used
to dissipate the force of incoming waves, and bulkheads
placed landward of the rip rap. Between 1963 and 1988, a
homeowners’ organization (the “Organization”) had leased
the tidelands from the Lummi Nation, giving waterfront prop-
erty owners the right to erect shore defense structures on the
tidelands; however, once the lease expired, both the Organiza-
tion and the individual Homeowners declined to renew the
lease.

   Under federal law, the upper boundary of any tidelands is
the mean high water (MHW) line, which is determined by
projecting onto the shore the average of all high tides over a
14466                UNITED STATES v. NICHOLSON
period of 18.6 years. Borax Consol. Ltd. v. City of Los Ange-
les, 296 U.S. 10, 26-27 (1935). Over time, the Sandy Point
shoreline has eroded significantly, so that as of January 2002,
the date of the most recent survey in the record, some of the
Homeowners’ shore defense structures sat seaward of the
MHW line and within the Lummi tidelands.3 Given the expi-
ration of the lease, the Homeowners do not have permission
from the United States or the Lummi Nation to maintain
structures on the tidelands, and they also lack permits to
maintain structures in navigable waters of the United States or
to discharge fill material into the waters of the United States.

   The United States Army Corps of Engineers, and later the
United States Attorney for the Western District of Washing-
ton, sent letters to the Homeowners demanding removal of the
structures or alternatively that the Homeowners enter into
agreements to lease the tidelands. When the Homeowners did
not remove the structures, the United States filed virtually
identical complaints against the separate Homeowners, alleg-
ing three causes of action: (1) trespass; (2) violation of § 10
of the Rivers and Harbors Appropriation Act of 1899 (RHA),
33 U.S.C. § 403; and (3) violation of § 301(a) of the Clean
Water Act (CWA), 33 U.S.C. § 1311(a).4 The Lummi Nation
intervened in the consolidated action to assert its interest as
the beneficial owner of the tidelands.

   In a series of partial summary judgment rulings, District
Judge Rothstein held that (1) the tidelands were owned by the
United States, not the state of Washington; (2) the erosion of
the Homeowners’ property was not caused by an avulsive
event inundating the uplands;5 and (3) the tideland boundary
  3
    Further complicating matters is the fact that the extent of the shore
changes seasonally, though mean high water stays relatively constant.
  4
    Although the United States originally sued six landowners, the govern-
ment and the Lummi Nation reached a settlement with one landowner and
entered into a consent decree with another.
  5
    Under the doctrine of avulsion, a sudden and abrupt change in the
shoreline—an avulsive event—does not alter the boundary line. New Jer-
                     UNITED STATES v. NICHOLSON                     14467
line was ambulatory and was not arrested by the Homeown-
ers’ shore defense structures, so that it lay where the MHW
line would be located but for the Homeowners’ structures.
Judge Rothstein then ruled on summary judgment that the
Homeowners were liable for trespass and violation of the
RHA, and that the Nicholsons had violated the CWA.
Although the United States had sued the other Homeowners
for violation of the CWA, it later dismissed those claims
against all but the Nicholsons.

   After finding liability, Judge Rothstein imposed an injunc-
tion under the RHA ordering the Homeowners to remove any
shore defense structures located seaward of the MHW line.
District Judge Leighton subsequently conducted a bench trial
to determine what penalties to impose on the Nicholsons for
the CWA violation. He imposed a $1500 fine—far less than
what the government sought—and ordered them to remove rip
rap below a certain point. Additionally, Judge Leighton heard
the Milners’ and Bennett/Boyd’s motion for attorneys’ fees
under the Equal Access to Justice Act (EAJA), 28 U.S.C.
§ 2412, which he denied.

   The Homeowners timely appealed, challenging the sum-
mary judgment rulings on the trespass, RHA, and CWA
claims, as well as the injunctive relief imposed by the district
court. The Homeowners also argue that the district court erred
in denying the EAJA motion. We address these arguments in
turn.

                                   II.

  The district court had jurisdiction over the trespass claims
under 28 U.S.C. § 1345, the RHA claims under 28 U.S.C.

sey v. New York, 523 U.S. 767, 784 (1998); California ex rel. State Lands
Comm’n v. United States, 805 F.2d 857, 864 (9th Cir. 1986). The Home-
owners do not appeal the district court’s ruling that the doctrine of avul-
sion does not apply.
14468                UNITED STATES v. NICHOLSON
§§ 1331, 1345 and 33 U.S.C. § 406, and the CWA claims
under 28 U.S.C. §§ 1331 and 1345. We have jurisdiction pur-
suant to 28 U.S.C. § 1291.

   We review the district court’s grant of summary judgment
de novo. Universal Health Servs., Inc. v. Thompson, 363 F.3d
1013, 1019 (9th Cir. 2004). We review a district court’s grant
of injunctive relief for abuse of discretion and will reverse if
the district court based its decision on an erroneous legal stan-
dard or a clearly erroneous finding of fact. Fortyune v. Ameri-
can Multi-Cinema, Inc., 364 F.3d 1075, 1079 (9th Cir. 2004).
The decision whether to award fees under the EAJA also is
reviewed for abuse of discretion. United States v. Marolf, 277
F.3d 1156, 1160 (9th Cir. 2002).

                                    III.

                                     A.

  Federal common law governs an action for trespass on
Indian lands. United States v. Pend Oreille Pub. Util. Dist.
No. 1, 28 F.3d 1544, 1549 n.8 (9th Cir. 1994); see also
Oneida County v. Oneida Indian Nation of New York State,
470 U.S. 226, 235-36 (1985). That law generally comports
with the Restatement of Torts, and in any event, Washington
law conforms to the Restatement definition of trespass.6 See
   6
     In some instances, “[c]ontroversies governed by federal law do not
inevitably require resort to uniform federal rules,” and it may be appropri-
ate to borrow from state law for the rule of decision. California ex rel.
State Lands Comm’n v. United States, 457 U.S. 273, 283 (1982). For
example, in Wilson v. Omaha Indian Tribe, the Supreme Court held that
although federal law determined the question of ownership of land contin-
uously held by the United States for an Indian tribe, state law could be
borrowed to provide the applicable rules of avulsion and accretion. 442
U.S. 653, 670-71, 673-74 (1979). While it is clear that the federal common
law of trespass applies here, it is less clear whether the application of the
common enemy doctrine, discussed below, should be decided based on a
uniform federal common law or borrowed Washington state law, which
                    UNITED STATES v. NICHOLSON                   14469
United States v. West, 232 F.2d 694, 699 (9th Cir. 1956) (cit-
ing Arizona case law and the Restatement (First) of Torts to
define trespass); Edwardsen v. Morton, 369 F. Supp. 1359,
1371 (D.D.C. 1973) (applying Restatement (Second) of Torts
to federal trespass action); United States v. Osterlund, 505 F.
Supp. 165, 167 (D.C. Colo. 1981) (same); cf. Bradley v. Am.
Smelting & Ref. Co., 709 P.2d 782, 785 (Wash. 1985) (quot-
ing Restatement (Second) of Torts definition of trespass).
Under the Restatement, a person is liable for trespass “if he
intentionally . . . causes a thing [to enter land in the posses-
sion of another], . . . [or] fails to remove from the land a thing
which he is under a duty to remove.” Restatement (Second)
of Torts § 158 (2009).

   The district court found it uncontested that portions of the
Homeowners’ shore defense structures were seaward of the
MHW line and therefore in Lummi tidelands. Nevertheless,
the Homeowners make three arguments that they cannot be
liable for trespass. First, they argue that Washington state, not
the United States, owns the tidelands; therefore, the United
States cannot properly assert an action for trespass against
them. Second, they contend that because their structures were
lawfully built landward of the MHW line—that is, on the
Homeowners’ property—they cannot be liable for trespass,
despite the movement of the tideland boundary. Finally, they
argue that the elements of intent and causation were not satis-
fied. We conclude that none of these arguments is correct.




holds that the doctrine does not apply to sea water. See Grundy v. Thur-
ston County, 117 P.3d 1089, 1094 (Wash. 2005). We note that it would
be anomalous for the Grundy decision to apply to other coastal property
owners in Washington, yet not to this small group of homeowners. Never-
theless, we need not decide the issue, because we conclude that the com-
mon enemy doctrine is inapplicable regardless of whether Grundy
provides the federal rule of decision.
14470                UNITED STATES v. NICHOLSON
                                     1.

   [1] The Homeowners’ ownership argument turns on the
effect of President Grant’s executive order and its force under
the “equal footing” doctrine. To put newly admitted states on
an “equal footing” with the original states, the doctrine creates
a strong presumption that newly admitted states acquire title
to lands under navigable waters upon their admission to state-
hood. Idaho v. United States, 533 U.S. 262, 272-73 (2001).
The presumption is rebutted (1) if such lands have been
reserved by the United States, and (2) if Congress recognizes
the reservation in a way that demonstrates an intent to rebut
the presumption. Id. at 273. According to the Homeowners,
because President Grant’s executive order could not perma-
nently reserve the tidelands for the Lummi, under the equal
footing doctrine, title passed to the state of Washington when
it became a state.7

   [2] Prior quiet title actions make clear that President
Grant’s executive order was sufficient to prevent ownership
from passing to Washington. In United States v. Romaine, the
  7
    The United States argues that the Homeowners cannot assert Washing-
ton state’s title in the tidelands because in a trespass action “[t]itle in a
third person may not be alleged by a defendant who is not in privity of
title with the third person,” and the Homeowners do not claim to be in
privity with the state. 75 Am. Jur. 2d Trespass § 62 (2009). However, this
applies where the plaintiff is the one in possession and, in moving for par-
tial summary judgment on the issue of ownership, the United States did
not present evidence showing that it or the Lummi Nation was currently
in possession of the tidelands. See Thomsen v. State, 422 P.2d 824, 827
(Wash. 1966) (“The presumption of the law that the person who has the
possession has the property may not be rebutted by evidence that the prop-
erty was in a third person, when offered as a defense by one who claims
no title and was a wrongdoer.”).
   The United States’ issue preclusion argument is similarly without merit,
since the prior cases that the government relies on do not involve the
Homeowners and the Homeowners are not subject to the binding effect of
the prior judgments. See Taylor v. Sturgell, 128 S. Ct. 2161, 2172-73
(2008) (describing the six circumstances in which a nonparty can be
bound by a prior decision).
                  UNITED STATES v. NICHOLSON              14471
United States sought to quiet title against individuals who had
bought Lummi tidelands from the state of Washington. 255 F.
253, 253 (9th Cir. 1919). This court held the president’s exec-
utive order to be decisive and rejected an argument that the
reservation extended only to the high-water mark. Id. at 259-
60. Romaine noted that when Washington was admitted as a
state, it disclaimed any right and title

    to all lands lying within said limits owned or held by
    any Indian or Indian tribes; and that until the title
    thereto shall have been extinguished by the United
    States, the same shall be and remain subject to the
    disposition of the United States and said Indian lands
    shall remain under the absolute jurisdiction and con-
    trol of the Congress of the United States.

Id. at 260 (quoting Act of Feb. 22, 1889, ch. 180, § 4, 25 Stat.
676, 677). United States v. Stotts similarly involved a suit by
the United States to quiet title in Lummi tidelands purchased
from the state. 49 F.2d 619, 619 (W.D. Wash. 1930). Distin-
guishing United States v. Holt State Bank, 270 U.S. 49
(1926), one of the earliest cases establishing the contours of
the equal footing doctrine, Stotts held that unlike in Holt the
Lummi had a specific declaration reserving the tidelands for
them. Stotts, 49 F.2d at 621. Stotts also noted that the Treaty
of Point Elliott clearly gave the Lummi and other tribes the
right to fish in their “usual and accustomed grounds and sta-
tions” and that possession of the tidelands was “a necessary
perquisite to the enjoyment of fishing.” Id. at 620-21. In more
recent litigation, we again gave effect to the 1873 executive
order as definitively establishing the boundaries of the Lummi
reservation, including the order’s reservation of tidelands.
United States v. Washington, 969 F.2d 752, 755-56 (9th Cir.
1992). Notably, in Washington, the state took the position that
the Lummi reservation extends to the low-tide line and did not
claim the tidelands. Id. at 753. In this lawsuit, the state has
expressly declined to claim ownership of the tidelands and to
intervene.
14472             UNITED STATES v. NICHOLSON
   [3] We have remarked before that stare decisis “applies
with special force to decisions affecting title to land,” given
the special reliance that such decisions command. Confeder-
ated Salish & Kootenai Tribes v. Namen, 665 F.2d 951, 960
(9th Cir. 1982); see also Minnesota Co. v. Nat’l Co., 70 U.S.
332, 334 (1865) (“Where questions arise which affect titles to
land it is of great importance to the public that when they are
once decided they should no longer be considered open. Such
decisions become rules of property, and many titles may be
injuriously affected by their change.”); Hart v. Massanari,
266 F.3d 1155, 1171 (9th Cir. 2001) (“Once a panel resolves
an issue in a precedential opinion, the matter is deemed
resolved, unless overruled by the court itself sitting en banc,
or by the Supreme Court.”). The Lummi and homeowners on
Sandy Point have long relied on the fact that the Lummi own
the tidelands. Until 1988, Homeowners leased the tidelands
from the Lummi, with both sides believing that the Lummi
owned the tidelands. We see no reason, then, to overturn 90
years of precedent, especially when the supposed title holder
has declined to claim ownership.

   Additionally, evaluating the executive order against con-
temporary case law, we find it sufficient to rebut the presump-
tion of the equal footing doctrine. As the Supreme Court has
explained, “the two-step test of congressional intent is satis-
fied when an Executive reservation clearly includes sub-
merged lands, and Congress recognizes the reservation in a
way that demonstrates an intent to defeat state title.” Idaho,
533 U.S. at 273 (citing United States v. Alaska, 521 U.S. 1,
41-46, 55-61 (1997) (Alaska (Arctic Coast))). Although “dis-
posals by the United States during the territorial period are not
lightly to be inferred,” Holt State Bank, 270 U.S. at 55,
because the two-step test of congressional intent is met, the
tidelands did not pass to Washington upon its admission to
statehood.

  [4] The first part of the test is easily met. Article VII of the
Treaty of Point Elliott provides that “[t]he President may
                       UNITED STATES v. NICHOLSON                        14473
hereafter, when in his opinion the interests of the Territory
shall require and the welfare of the said Indians be promoted,
remove them from either or all of the special reservations
hereinbefore made to the said general reservation, or such
other suitable place within said Territory as he may deem fit.”
12 Stat. at 929. Thus, in ratifying the Treaty, Congress gave
the President the discretionary power to alter the boundaries
of the reservation;8 he later exercised these powers by explic-
itly extending the reservation to the low-water mark, thereby
including the tidelands. Cf. Alaska v. United States, 545 U.S.
75, 101-02 (2005) (Alaska (Glacier Bay)) (finding that execu-
tive proclamation reserving submerged lands as part of
national monument met first prong of congressional intent
test).

   [5] When Congress admitted Washington to statehood, it
was aware that the President’s executive order added the tide-
lands to the reservation. See Alaska (Arctic Coast), 521 U.S.
at 45 (finding that the President’s executive order “placed
Congress on notice that the President had construed his reser-
vation authority to extend to submerged lands and had exer-
cised that authority to set aside uplands and submerged lands
in the Reserve”). And while Congress admitted Washington
on an equal footing, 25 Stat. at 679, it also recognized the
validity of the executive order reservation by requiring Wash-
  8
   Treaties and other agreements with Indians are liberally construed in
favor of the Indians. Choctaw Nation v. United States, 318 U.S. 423, 431-
32 (1943) (“Of course treaties are construed more liberally than private
agreements[ ] . . . . Especially is this true in interpreting treaties and agree-
ments with Indians; they are to be construed, so far as possible, in the
sense in which the Indians understood them, and ‘in a spirit which gener-
ously recognizes the full obligation of this nation to protect the interests
of a dependent people’ ” (citations omitted)). The President’s power to
“remove” the tribes from the specified reservations to “such other suitable
place . . . as he may deem fit” therefore encompasses the power to expand
the boundaries of the reservation, since the President has the discretion to
deem an expanded reservation a suitable replacement for the current one
and “remove” the tribes from the smaller reservation to the expanded one.
14474             UNITED STATES v. NICHOLSON
ington state to “forever disclaim all right and title . . . to all
lands . . . owned or held by any Indian or Indian tribes.” Id.
at 677. This proviso was written more broadly than Con-
gress’s specific recognition of ownership over the National
Petroleum Reserve in Alaska (Arctic Coast), see 521 U.S. at
41-42, but a broad congressional statement can still be a clear
expression of intent. In Alaska (Glacier Bay), the Supreme
Court held that an exception that prevented the transfer of
“lands withdrawn or otherwise set apart as refuges or reserva-
tions for the protection of wildlife” to the state of Alaska was
a sufficient indication of intent so as to defeat state title to
submerged lands in the Glacier Bay National Monument. 545
U.S. at 105 (quoting the Alaska Statehood Act, Pub. L. No.
85-508, § 6(e), 72 Stat. 339, 341 (1958)). As in Alaska (Gla-
cier Bay), Congress made it abundantly clear here that Wash-
ington would not have title to the lands in question, thereby
satisfying the second step of the congressional intent test.

   [6] Historically, the Lummi and other Pacific Northwest
tribes have depended heavily on fishing and digging for shell-
fish as a means of subsistence. See Stotts, 49 F.2d at 620-21;
Washington v. Wash. State Commercial Passenger Fishing
Vessel Ass’n, 443 U.S. 658, 665-67 (1979). President Grant’s
reservation of the tidelands thus served to promote the tribe’s
access to fishing and shellfish, and the welfare of the tribe
more generally. Longstanding precedent has established that
the tidelands were reserved for the Lummi, and both the tribe
and others have relied on this understanding for years. But
even were there no such precedent, the executive order reserv-
ing the tidelands was promulgated pursuant to congressional
authority and subsequently recognized by Congress in a way
that indicates a clear intent to prevent title from passing to the
state of Washington. We therefore hold that the United States
owns the tidelands and holds them in trust for the Lummi.
                     UNITED STATES v. NICHOLSON                      14475
                                    2.

    The problem of riparian and littoral property boundaries is
a recurring and difficult issue. These disputes can be espe-
cially complicated where the land borders tidal waters,
because the waters fluctuate dramatically and because private
title claims often have to be balanced against federal and state
interests in the ownership and use of the submerged lands. At
issue in the Homeowners’ second challenge to the trespass
claim are two competing common law principles. On the one
hand, courts have long recognized that an owner of riparian
or littoral property must accept that the property boundary is
ambulatory, subject to gradual loss or gain depending on the
whims of the sea.9 See, e.g., County of St. Clair v. Lovingston,
90 U.S. 46, 68-69 (1874). On the other hand, the common law
also supports the owner’s right to build structures upon the
land to protect against erosion. See, e.g., Cass v. Dicks, 44 P.
113, 114 (Wash. 1896) (“If a landowner whose lands are
exposed to inroads of the sea[ ] . . . erects sea walls or dams
for the protection of his land, and by so doing causes the tide,
the current, or the waves to flow against the land of his neigh-
bor . . . [he] is not responsible in damages to the latter, as he
has done no wrong having acted in self-defense, and having
a right to protect his land.” (citation omitted)). In this case, the
Homeowners’ land has eroded away so dramatically that the
ambulatory tideland boundary has reached and become fixed
at their shore defense structures. While the Homeowners can-
not be faulted for wanting to prevent their land from eroding
away, we conclude that because both the upland and tideland
owners have a vested right to gains from the ambulation of
the boundary, the Homeowners cannot permanently fix the
  9
   While the rights and duties of riparian landowners—those with land
fronting a river or stream—can differ from those of littoral landowners—
those with property fronting an ocean, sea, or lake—the rules often over-
lap and sometimes the distinction is elided altogether. See, e.g., Tusher v.
Gabrielsen, 80 Cal. Rptr. 2d 126, 146-47 (Ct. App. 1998); Thies v. How-
land, 380 N.W.2d 463, 288 n.2 (Mich. 1985); but see In re Opinions of
the Justices, 106 A. 865, 868-69 (Me. 1919) (stating that a riparian owner
may lower a stream so long as the use is reasonable but that a littoral
owner may not draw down a lake below the natural level).
14476             UNITED STATES v. NICHOLSON
property boundary, thereby depriving the Lummi of tidelands
that they would otherwise gain.

    [7] Under the common law, the boundary between the tide-
lands and the uplands is ambulatory; that is, it changes when
the water body shifts course or changes in volume. See Jef-
feris v. East Omaha Land Co., 134 U.S. 178, 189 (1890); Cal-
ifornia ex rel. State Lands Comm’n v. United States, 805 F.2d
857, 864 (9th Cir. 1986); United States v. Boynton, 53 F.2d
297, 298 (9th Cir. 1931). The uplands owner loses title in
favor of the tideland owner—often the state—when land is
lost to the sea by erosion or submergence. The converse of
this proposition is that the littoral property owner gains when
land is gradually added through accretion, the accumulation
of deposits, or reliction, the exposure of previously sub-
merged land. See County of St. Clair, 90 U.S. at 68-69; Jef-
feris, 134 U.S. at 189; 65 C.J.S. Navigable Waters § 95
(2009). These rules date back to Roman times, and have been
noted in Blackstone’s Commentaries and many other common
law authorities and cases. See County of St. Clair, 90 U.S. 66-
67 (citing inter alia the Institutes of Justinian, the Code Napo-
leon, and Blackstone’s Commentaries); John M. Gould, A
Treatise on the Law of Waters 306-08 (3d ed. 1900) (“Land
formed by alluvion, or the gradual and imperceptible accre-
tion from the water, and land gained by reliction, or the grad-
ual and imperceptible recession of the water, belong to the
owner of the contiguous land to which the addition is made.
. . . Conversely land gradually encroached upon by navigable
waters ceases to belong to the former owner.”); 3 Emory
Washburn, A Treatise on the American Law of Real Property
75 (6th ed. 1902) (“[T]he boundary line of an owner’s land
bordering upon the sea varies with the gradual increase or
diminution of quantity by the addition of alluvion, or by the
encroachments of the water upon the land, the line of the
shore varying accordingly.”).

  [8] Importantly, the upland owner’s right to accretions is a
vested right and “rests in the law of nature.” County of St.
                  UNITED STATES v. NICHOLSON               14477
Clair, 90 U.S. at 68. It is justified in large part because the
upland owner’s land is subject to erosion. As the Supreme
Court stated in County of St. Clair,

    The riparian right to future alluvion is a vested right.
    It is an inherent and essential attribute of the original
    property. The title to the increment rests in the law
    of nature. It is the same with that of the owner of a
    tree to its fruits, and of the owner of flocks and herds
    to their natural increase. The right is a natural, not a
    civil one. The maxim ‘qui sentit onus debet sentire
    commodum’ [‘he who enjoys the benefit ought also
    to bear the burdens’] lies at its foundation. The
    owner takes the chances of injury and of benefit aris-
    ing from the situation of the property. If there be a
    gradual loss, he must bear it; if, a gradual gain, it is
    his.

Id. at 68-69; see also Nebraska v. Iowa, 143 U.S. 359, 360-61
(1892) (“Every proprietor whose land is thus bounded [by
water] is subject to loss by the same means which may add
to his territory; and, as he is without remedy for his loss in
this way, he cannot be held accountable for his gain.” (quot-
ing New Orleans v. United States, 35 U.S. (10 Pet.) 662, 717
(1836))); Bonelli Cattle Co. v. Arizona, 414 U.S. 313, 326
(1973) (“Since a riparian owner is subject to losing land by
erosion beyond his control, he should benefit from any addi-
tion to his lands by the accretions thereto which are equally
beyond his control.”), overruled on other grounds by Oregon
ex rel. State Land Board v. Corvallis Sand & Gravel Co., 429
U.S. 363 (1977).

   [9] By this logic, both the tideland owner and the upland
owner have a right to an ambulatory boundary, and each has
a vested right in the potential gains that accrue from the
movement of the boundary line. The relationship between the
tideland and upland owners is reciprocal: any loss experi-
enced by one is a gain made by the other, and it would be
14478              UNITED STATES v. NICHOLSON
inherently unfair to the tideland owner to privilege the forces
of accretion over those of erosion. Indeed, the fairness ratio-
nale underlying courts’ adoption of the rule of accretion
assumes that uplands already are subject to erosion for which
the owner otherwise has no remedy.

   Some courts have justified the rule of accretion by noting
that it is in the interest of the community that land have an
owner and be put to “productive use.” See Bd. of Trustees of
the Internal Improvement Fund v. Medeira Beach Nominee,
Inc., 272 So. 2d 209, 213 (Fla. Dist. Ct. App. 1973); Brainard
v. State, 12 S.W.3d 6, 18 (Tex. 1999). While this could be
seen as supporting the notion that dry uplands should be val-
ued more than tidelands, we decline to hold that the use of
uplands is inherently more valuable than the use to which
tidelands can be put. As was already noted, the tidelands have
played an important role in the Lummi’s traditional way of
life, and in most other areas, the tidelands are held by the state
in trust for the public. See Illinois Central R.R. Co. v. Illinois,
146 U.S. 387, 436-37 (1892). These interests are substantial,
and the uses they represent are not obviously less “produc-
tive.” See Shively v. Bowlby, 152 U.S. 1, 57 (1894) (“[Lands
under tide waters] are of great value to the public for the pur-
poses of commerce, navigation, and fishery. Their improve-
ment by individuals, when permitted, is incidental or
subordinate to the public use and right.”). Thus, both the
Lummi and the Homeowners must accept that the ambulatory
boundary is “an inherent and essential attribute of the original
property,” County of St. Clair, 90 U.S. at 68, and that both the
tidelands and the uplands are subject to diminishment and
expansion based on the forces of the sea.

   [10] The Homeowners concede that the tideland boundary
is ambulatory, but only to a point. According to the Home-
owners, once the MHW line intersects the face of their
defense structures, the boundary becomes fixed and remains
so unless the tide line overtops the structures or recedes. The
Homeowners rightly note that the common law permits them
                     UNITED STATES v. NICHOLSON                      14479
to erect shore defense structures on their property to prevent
erosion. They contend that they lawfully did just that, build-
ing landward of the MHW line, and cannot be liable for the
movement of the tideland boundary. In particular, the Home-
owners draw support for their position from the common
enemy doctrine, which provides that “[a] man may raise an
embankment on his own property to prevent the encroach-
ments of the sea, although the fact of his doing so may be to
cause the water to beat with violence against the adjoining
lands, thereby rendering it necessary for the adjoining land-
owner to enlarge or strengthen his defenses.” Revell v. People,
52 N.E. 1052, 1059 (Ill. 1898) (quotation marks and citation
omitted).

   [11] Typically, the common enemy doctrine applies as a
defense to nuisance or trespass actions where a property
owner has caused surface waters—the “common enemy” of
all landowners—to invade a neighbor’s property.10 See, e.g.,
Cass v. Dicks, 44 P. 113, 114 (Wash. 1896) (“[S]urface water,
caused by the falling of rain or the melting of snow, and that
escaping from running streams and rivers, is regarded as an
  10
     Many jurisdictions have dispensed with the doctrine altogether and
instead apply a rule of reasonableness, under which “each possessor is
legally privileged to make a reasonable use of his land, even though the
flow of surface waters is altered thereby and causes some harm to others,
but incurs liability when his harmful interference with the flow of surface
waters is unreasonable.” Armstrong v. Francis Corp., 120 A.2d 4, 8 (N.J.
1956); see, e.g., Weinberg v. N. Alaska Dev. Corp., 384 P.2d 450, 452
(Alaska 1963); Bunch v. Coachella Valley Water Dist., 935 P.2d 796, 801
(Cal. 1997); Rodrigues v. State, 472 P.2d 509, 516 (Haw. 1970); see gen-
erally, Wendy B. Davis, Reasonable Use Has Become the Common
Enemy, 9 Alb. L. Envtl. Outlook J. 1, 9-10 (2004) (noting that 21 states
have adopted the “reasonable use” rule). While Washington has retained
the doctrine, it has modified the rule so that property owners must exercise
due care by “acting in good faith and avoiding unnecessary damage to the
property of others,” Currens v. Sleek, 983 P.2d 626, 629-30 (Wash. 1999),
and by making the rule inapplicable to sea water. Grundy, 117 P.3d at
1094. It is far from clear, then, that the common enemy rule, as advocated
by the Homeowners, is even the dominant view.
14480             UNITED STATES v. NICHOLSON
outlaw and a common enemy, against which any one may
defend himself, even though by doing so injury may result to
others.”). The doctrine therefore does not apply here. On the
one hand, the injury complained of is not the diversion of
water onto the tidelands; rather, it is the physical encroach-
ment of the shore defense structures themselves. With the
exception of Revell, which held that a waterfront property
owner had no right to erect structures on submerged land
owned by the state, 52 N.E. at 1060, all the cases cited by the
Homeowners concern disputes over structures diverting
waters onto a neighbor’s land, not the maintenance of struc-
tures on the neighbor’s land. See Lamb v. Reclamation Dist.
No. 108, 14 P. 625, 626-27 (Cal. 1887); Miller v. Lezerich, 49
S.W.2d 404, 406 (Tex. 1932). On the other hand, the rule is
inapposite because the water is not acting as a “common
enemy” of the parties involved. The tide line is an inherent
attribute of the properties at issue, since it dictates where the
tidelands end and the uplands begin. That the boundary is
ambulatory does not make it a common enemy, since any
movement seaward or landward is to the benefit of one party
and the detriment of the other. It is unfortunate that the
boundary line increasingly has encroached on the Homeown-
ers’ property, but they cannot claim that the common enemy
doctrine allows them to fix permanently the tideland bound-
ary.

   [12] The Homeowners have the right to build on their prop-
erty and to erect structures to defend against erosion and
storm damage, but all property owners are subject to limita-
tions in how they use their property. The Homeowners cannot
use their land in a way that would harm the Lummi’s interest
in the neighboring tidelands. Given that the Lummi have a
vested right to the ambulatory boundary and to the tidelands
they would gain if the boundary were allowed to ambulate,
the Homeowners do not have the right to permanently fix the
property boundary absent consent from the United States or
the Lummi Nation. The Lummi similarly could not erect
structures on the tidelands that would permanently fix the
                     UNITED STATES v. NICHOLSON                      14481
boundary and prevent accretion benefitting the Homeowners.
Although the shore defense structures may have been legal as
they were initially erected, this is not a defense against the
trespass action nor does it justify denying the Lummi land that
would otherwise accrue to them.

   [13] We emphasize that this does not mean property own-
ers cannot erect shore defense structures on their property or
take other action to prevent erosion. Nor does it mean that the
Homeowners must necessarily remove their structures, if they
can reach an agreement with the Lummi Nation and the
United States that allows the structures to remain. Rather, we
hold only that the Homeowners have no defense to a trespass
action because they are seeking to protect against erosion.11
Once the shore has eroded so dramatically that the property
owner’s shore defense structures fix the ambulatory boundary,
the upland owner cannot expect to permanently maintain the
boundary there without paying damages to the tideland owner
or working out an agreement with the tideland owner. Home-
owners on Sandy Point previously had leased the tidelands
from the Lummi, and there is no reason the Homeowners
could not similarly seek to negotiate a new agreement now.
  11
     Amicus curiae Building Industry Legal Defense Foundation (“BILD”)
argues that such a rule will have dramatically harmful consequences,
given the many coastal properties with shore defense structures. This over-
estimates the reach of our opinion, however. Because of the equal footing
doctrine and the Submerged Lands Act, 43 U.S.C. § 1311, the states hold
title to most of the tidelands. Most disputes that arise between the states
and littoral property owners over tideland boundaries and the use of tide-
lands are ultimately a matter for state courts to adjudicate under state law.
The states, of course, must consider the public interest—not just those of
waterfront property owners—in deciding how to manage their tidelands,
as they already have been doing. As with many property disputes, those
between tideland holders and littoral property owners will not be easy to
resolve and they may simply require the parties to compromise, even if
that means not everyone is entirely satisfied with the results.
14482             UNITED STATES v. NICHOLSON
                               3.

   It is undisputed that as of the 2002 survey, some of the
Homeowners’ shore defense structures sat seaward of the
MHW line. The Homeowners nevertheless argue that they
cannot be liable for trespass because they did not intend the
structures to trespass and because the trespass was caused by
the erosion of the shore and resulting movement of the bound-
ary, not by the Homeowners.

   [14] However, as the district court noted, to be liable for
trespass, the Homeowners need not have intended the actual
trespass. Rather, the intent requirement is satisfied because
the government requested that the encroaching parts of the
structures be removed, but the Homeowners failed to do so.
See New York State Energy Research & Dev. Auth. v. Nuclear
Fuel Servs., Inc., 561 F. Supp. 954, 974 (W.D.N.Y. 1983)
(“In the case of trespass through the continuing presence of
chattels on another’s land, the requisite intent does not arise
until the duty to remove the chattels arises, which does not
occur until a demand for removal has been made.”); see also
Restatement (Second) of Torts § 161; 75 Am. Jur. 2d Trespass
§ 19 (2009) (“A trespass may be committed by the continued
presence on the land of a structure, chattel, or other thing that
the actor or a predecessor in legal interest has placed on the
land and failed to remove.”). And although the Homeowners
did not cause the movement of the boundary line, they can
still be liable for the structures even after the boundary moved
across the structures. It is enough that the Homeowners
caused the structures to be erected and that the structures sub-
sequently rested on the tidelands. See Restatement (Second)
of Torts § 161, cmts. b, e.

    [15] Given that the United States, not Washington, holds
title to the tidelands and that the Homeowners cannot perma-
nently fix the tideland boundary, it quickly follows that the
Homeowners are liable for trespass. The district court was
                  UNITED STATES v. NICHOLSON               14483
correct, then, in finding in favor of the United States and
Lummi Nation as to the trespass claim.

                               B.

   [16] Turning next to the RHA claim, there are three ways
in which a defendant could violate § 10 of the RHA. The first
clause of § 10 prohibits the creation of “any obstruction not
affirmatively authorized by Congress[ ] to the navigable
capacity of any of the waters of the United States.” 33 U.S.C.
§ 403. Clauses two and three respectively make it unlawful to
“build or commence the building of any wharf, pier, dolphin,
boom, weir, breakwater, bulkhead, jetty, or other structures in
any port, roadstead, haven, harbor, canal, navigable river, or
other water of the United States . . . except on plans recom-
mended by the Chief of Engineers and authorized by the Sec-
retary of the Army” or to “excavate or fill, or in any manner
to alter or modify the course, location, condition, or capacity
of . . . the channel of any navigable water of the United States,
unless the work has been recommended by the Chief of Engi-
neers and authorized by the Secretary of the Army prior to
beginning the same.” Id.

   Under the RHA the navigable waters of the United States
means “all places covered by the ebb and flow of the tide to
the mean high water (MHW) mark in its unobstructed, natural
state.” Leslie Salt Co. v. Froehlke, 578 F.2d 742, 753 (9th Cir.
1978); see also 33 C.F.R. §§ 322.2(a), 329.4, 329.12(a)(2).
Notably, courts have “consistently found [the RHA’s] cover-
age to be broad,” Wyandotte Transp. Co. v. United States, 389
U.S. 191, 201 (1967); see also Sanitary Dist. Co. of Chicago
v. United States, 266 U.S. 405, 429 (1925) (calling the RHA
“a broad expression of policy in unmistakable terms”), and
“read the [RHA] charitably in light of the purpose to be
served.” United States v. Republic Steel Corp., 362 U.S. 482,
491 (1960).

   The Homeowners concede that they do not have authoriza-
tion to maintain structures in the navigable waters of the
14484                UNITED STATES v. NICHOLSON
United States. Given that at least some of their shore defense
structures lie seaward of the MHW line, the issue on appeal
is whether the district court properly ruled that the Homeown-
ers had violated § 10 by not removing their shore defense
structures from the tidelands.

   [17] Although § 10 does not explicitly mention the mainte-
nance of structures in navigable waters, in the sense of keep-
ing structures in place, we have interpreted the RHA as
making unlawful the failure to remove structures prohibited
by § 10, even if they were previously legal. See United States
v. Alameda Gateway Ltd., 213 F.3d 1161, 1167 (9th Cir.
2000) (“Gateway’s assertion that the Corps cannot remove a
lawfully erected structure is equally unavailing. . . . the RHA
allows the United States to remove structures that were once
erected lawfully but subsequently found to be obstructions.”).
This makes sense in light of the RHA’s concern with insuring
that navigable waterways remain free of obstruction, because
even initially legal structures can subsequently interfere with
navigation. See, e.g., United States v. New York Cent. R.R.,
252 F. Supp. 508, 511 (D. Mass. 1965) (finding landward
remnants of previously legal bridge an obstruction), aff’d per
curiam, 358 F.2d 747 (1st Cir. 1966). The Homeowners’
structures may have been legal as initially built, but because
of the movement of the tidal boundary they now sit in naviga-
ble waters and are obstructions.12

   [18] The Homeowners argue that Alameda Gateway is
inapplicable, because it concerns the first clause of § 10, and,
according to them, the shore defense structures do not inter-
fere with navigation. However, structures violating clauses
  12
     The Corps’ regulations confirm that structures may be obstructions
without regard to how the structures came to be in navigable waters. The
Corps generally requires a permit “for structures and/or work in or affect-
ing navigable waters,” without reference to whether the structure is being
initially erected in navigable waters or has already been sitting there. 33
C.F.R. § 322.3(a).
                  UNITED STATES v. NICHOLSON               14485
two or three are presumed to be obstructions under the first
clause. Alameda Gateway, 213 F.3d at 1165; Sierra Club v.
Andrus, 610 F.2d 581, 596 (9th Cir. 1979), rev’d on other
grounds sub nom. California v. Sierra Club, 451 U.S. 287
(1981) (holding that there is no implied private right of action
under § 10 and thus declining to reach the merits). That is,
clauses two and three have been interpreted as “a legislative
enumeration of specific obstructions to navigable capacity
that require Corps authorization” to be legal, Andrus, 610
F.2d at 594, with the Corps having discretion to “determine
what in the particular cases constitute[s] an unreasonable
obstruction.” Id. at 596 (quoting Wisconsin v. Illinois, 278
U.S. 367, 413 (1929)). There is no need, then, for the Corps
or the courts to determine first that the Homeowners’ struc-
tures obstruct navigable capacity, since the structures obvi-
ously qualify as a “breakwater, bulkhead, . . . or other
structure” under clause two and modify the course, location,
condition, and capacity of the Strait under clause three. 33
U.S.C. § 403. The Homeowners are therefore required to have
Corps authorization; because they have maintained their
structures in the tidelands without such authorization, they
can be liable under the RHA.

   BILD argues that under the RHA navigable waters do not
extend to the MHW line in its “unobstructed, natural state,”
because Leslie Salt stated that this jurisdictional line “is dic-
tated by the principle . . . that one who develops areas below
the MHW line does so at his peril.” 578 F.2d at 753. Accord-
ing to BILD, since the Homeowners claim they built above
the MHW line, Leslie Salt is inapplicable. On the one hand,
whether navigable waters reach the MHW in its unobstructed
state or in its obstructed state is irrelevant here, because the
Homeowners are liable either way. The topographic survey
maps submitted by the government show that at least some rip
rap from the shore defense structures sits below the MHW
line, and that rip rap has not so obstructed the movement of
the tide that it is prevented from flowing landward of this
scattered rip rap. So even assuming an obstruction could pre-
14486                UNITED STATES v. NICHOLSON
vent the movement of the MHW line under the RHA, the
Homeowners have still violated clause two of § 10.

   On the other hand, this argument ignores the RHA’s central
concern, which is to insure that the nation’s waterways remain
navigable and free of obstruction. The nation’s navigable
waterways, of course, can change, and with it the Corps’
jurisdiction. See, e.g., Swanson v. United States, 789 F.2d
1368 (9th Cir. 1986) (finding Corps had jurisdiction over sub-
sequently flooded area). Structures that were previously above
the MHW line can become subject to Corps’ regulation
because the tide line has moved, and if those structures pre-
vent the MHW line from achieving its unobstructed, natural
state they can pose a serious risk to navigation. A structure
should not be exempt from regulation because it so signifi-
cantly displaces navigable waters that the waters are perma-
nently penned in. Just as one who develops below the MHW
line “does so at his peril,” those who build too close to the
MHW line also run the risk that their structures eventually
may become obstructions and be subject to regulation by the
Corps.13

   [19] The Homeowners’ structures additionally violate
clause three of § 10, without regard to whether or not one
considers the waters in their unobstructed state. In certain cir-
cumstances a structure or activity can still be a violation of
clauses one or three of § 10 even if the structure or activity
is not located in navigable waters. See United States v. Sexton
Cove Estates, Inc., 526 F.2d 1293, 1298 (5th Cir. 1976). As
the Fifth Circuit has put it, for the most part § 10 has “no
locality assigned to its prohibitions.” Id.
  13
    As in Leslie Salt, we express no opinion as to whether or at what point
the government may be estopped from asserting its jurisdiction because
land has long ago been filled in, as was the case in United States v. Stoeco
Homes, Inc., 498 F.2d 597, 610-11 (3d Cir. 1974). See 578 F.2d at 753.
There is no indication here that the United States excessively delayed its
enforcement efforts.
                  UNITED STATES v. NICHOLSON              14487
    It prohibits any obstruction to navigable capacity.
    There is no suggestion that an obstruction whose
    source is above [the MHW line] escapes prosecution.
    It prohibits the alteration or modification of the
    course, condition, location or capacity of a navigable
    water. There is not the slightest intimation that an
    alteration or modification whose source is above [the
    MHW line] is any less an alteration or modification.
    There is nothing in the language of the statute nor
    the logic of its implementation which creates this
    barrier beyond which the Corps is ubiquitously pow-
    erless. Indeed, such a limitation would thwart the
    design of the statute.

Id. at 1298-99; see also 33 C.F.R. § 322.3(a) (“Structures or
work outside [the navigable waters of the United States] are
subject to [§ 10] if these structures or work affect the course,
location, or condition of the waterbody in such a manner as
to impact on its navigable capacity.”). Under clause three,
even though the tide line does not extend past the Homeown-
ers’ shore defense structures because the Homeowners have
successfully prevented the Strait from advancing landward,
the structures “alter or modify the course, location, condition,
or capacity of” the Strait, since the flow of the waters is lim-
ited by the structures. 33 U.S.C. § 403. The Homeowners are
therefore liable on this alternative basis as well.

   [20] Because the Homeowners have maintained at least part
of their shore defense structures below the MHW line, and
because the structures alter the course, location, condition, or
capacity of the Strait, they are required to obtain Corps’
authorization or face liability. Contrary to the Homeowners’
claim, they need not have intended to violate the RHA; it is
sufficient under Alameda Gateway that they intentionally
erected structures that became obstructions. See 213 F.3d at
1167. The district court therefore appropriately found liabil-
ity, and its imposition of an injunction under § 12 of the RHA,
33 U.S.C. § 406, was not an abuse of discretion, given the
14488                 UNITED STATES v. NICHOLSON
standard for injunctions under § 12. See United States v.
Stoeco Homes, Inc., 498 F.2d 597, 611 (3d Cir. 1974) (“No
balancing of interest or need to show irreparable injury is
required when an injunction is sought under § 12 to prevent
erection or seek removal of an unlawful structure.”).

                                     C.

   [21] The CWA prohibits the discharge of any dredged or
fill material into “navigable waters” unless authorized by the
Corps. See 33 U.S.C. §§ 1311, 1344. However, the scope of
the Corps’ regulatory authority under the CWA and RHA is
not the same, in part because the definition of “navigable
waters” is broader under the CWA and encompasses all “wa-
ters of the United States.” 33 U.S.C. § 1362(7); Leslie Salt,
578 F.2d at 754-55. Instead of using the MHW line, the
Corps’ regulations define its CWA jurisdiction over tidal
waters by reference to the “high tide line,” 33 C.F.R.
§ 328.4(b)(1), which, in turn, is defined as “the line of inter-
section of the land with the water’s surface at the maximum
height reached by a rising tide.”14 33 C.F.R. § 328.3(d).

   The district court found on summary judgment that the
Nicholsons had violated the CWA, because, in the course of
reconstructing their shore defense structures, they discharged
fill material below where the high tide line would fall in its
   14
      Locally, the policy of the Seattle District of the Corps has been to
draw the high tide line at the mean higher high water (MHHW) line,
which is calculated by averaging over 18.6 years the highest of the two
high tides that occur in a day and projecting that line onto the shore. Leslie
Salt, 878 F.2d at 746. Because the two daily Pacific coast tidal cycles can
vary greatly in height, the difference between the MHHW line and the
MHW line—the average of both high tides occurring in a day—can be rel-
atively large on the west coast of the United States. Id. In fashioning a
remedy for the CWA violation, Judge Leighton took the Corps’ local
enforcement policy into account, but, contrary to the government’s posi-
tion, this does not necessarily conflict with what Judge Rothstein found on
summary judgment.
                  UNITED STATES v. NICHOLSON               14489
unobstructed, natural state without a permit. In so ruling, the
district court again relied on the holding from Leslie Salt that
“the MHW line is to be fixed in accordance with its natural,
unobstructed state.” 578 F.2d at 753. However, while Leslie
Salt applied this rule to the definition of navigable waters
under the RHA, it was more circumspect as to what the limits
of navigable waters and the Corps’ jurisdiction are under the
CWA. The district court in Leslie Salt had held that navigable
waters under the CWA extended to the MHHW line in its
unobstructed, natural state. Sierra Club v. Leslie Salt Co., 412
F. Supp. 1096, 1103 (N.D. Cal. 1976). But we declined to
hold that the waters of the United States extended to all places
the water would theoretically reach, partially out of concerns
that such a ruling swept too broadly and unnecessarily
included “fast land” or “improved solid upland.” See Leslie
Salt, 578 F.2d at 754. Since we could decide Leslie Salt by
addressing only whether the particular waters in question
were subject to regulation by the Corps, we did not address
the ultimate question of what constitutes the outer limit of the
Corps’ CWA jurisdiction. Id. at 756.

   [22] This case presents more squarely the question of how
far the Corps’ CWA jurisdiction extends. Leslie Salt
addressed whether certain waters diked off from the San Fran-
cisco Bay constituted waters of the United States. 578 F.2d at
756. Here there is a question as to whether any water actually
reaches the area at issue, and if not, whether it is still subject
to regulation by the Corps. The parties in Leslie Salt agreed
that the Corps’ jurisdiction does not extend to property that
was dry, solid upland as of the date of the passage of the
CWA. See id. at 754. In the same vein, the Corps has stated
that it does not intend to assert jurisdiction over lands that
once were submerged but which have been transformed into
dry land. See 42 Fed. Reg. 37128 (July 19, 1977). While we
do not purport to decide the full extent of the Corps’ CWA
regulatory authority, we find this approach persuasive. Any
discharge on fast land would not actually be in the waters of
the United States, and it would be potentially unfair to occu-
14490                UNITED STATES v. NICHOLSON
pants of such land to hold them to the strictures of the CWA
if the land has long been dry. Even if land has been main-
tained as dry through artificial means, if the activity does not
reach or otherwise have an effect on the waters, excavating,
filling and other work does not present the kind of threat the
CWA is meant to regulate.

   [23] This does not mean that fast land cannot subsequently
become submerged by the waters of the United States. As the
Corps’ regulations acknowledge, gradual changes to the bed
of a body of water will change the boundaries of the waters
of the United States. 33 C.F.R. § 328.5. But if land was dry
upland at the time the CWA was enacted, it will not be con-
sidered part of the waters of the United States unless the
waters actually overtake the land, even if it at one point had
been submerged before the CWA was enacted or if there have
been subsequent lawful improvements to the land in its dry
state.15 In short, in such a situation, the waters of the United
States are demarcated by the reach of the high tide line, but
not as it would be in its unobstructed, natural state if the fill
or obstruction was in place at the time the CWA was enacted
or if there was a legally authorized filling or improvement
done after the enactment of the CWA.
   15
      This would not change the fact that waters which were in the past nav-
igable are still considered such, even if they are no longer navigable in
fact. See United States v. Appalachian Elec. Power Co., 311 U.S. 377, 408
(1940) (“When once found to be navigable, a waterway remains so.”); 33
C.F.R. § 328.3(a)(1). We also reiterate Leslie Salt’s admonition that the
full extent of the Corps’ CWA jurisdiction over waters of the United
States “is in some instances not limited to the MHW or the MHHW line.”
Id. at 742. For example, where there are adjacent wetlands or intermittent
streams, the Corps still has jurisdiction, even though these areas are
beyond the normal ebb and flow of the tide. See, e.g., United States v. Riv-
erside Bayview Homes, Inc., 474 U.S. 121, 139 (1985); United States v.
Moses, 496 F.3d 984, 989 (9th Cir. 2007). Additionally, some discharges
on dry land can be CWA violations. See Leslie Salt, 578 F.2d at 753 n.12
(citing United States v. Holland, 373 F. Supp. 665 (M.D.Fla. 1974), as an
example of a discharge above MHHW line that violated CWA).
                  UNITED STATES v. NICHOLSON              14491
   [24] Applying that boundary here, it is unclear from the
evidence presented at summary judgment whether the high
tide line actually reached the area where the Nicholsons exca-
vated and filled. Pictures of the bulkhead reconstruction show
that the rip-rap revetment seaward of the bulkhead may have
successfully prevented the tide from reaching the area under
construction. The construction diagrams show an intent to
excavate to a depth that would be below the high tide line if
one ignored the existence of the revetment. But if the revet-
ment was in place prior to the enactment of the CWA or
legally built on dry land after the passage of the CWA, then
it must be considered as it actually exists. While the parties
seem to agree that the revetment was built in 1982 by the
Nicholsons’ predecessor in interest, on summary judgment the
government did not present evidence showing that the revet-
ment was not lawfully built on dry land beyond the reach of
the high tide line. There was also no evidence that during the
reconstruction of the bulkhead, the Nicholsons placed addi-
tional rip rap seaward of the revetment or that their activities
otherwise led to the discharge of material below the high tide
line, as it actually existed. The government therefore did not
carry its burden of showing that the Nicholsons had violated
the CWA by discharging material into waters of the United
States. Accordingly, we reverse the grant of summary judg-
ment on this claim and remand for further proceedings.

   Although the CWA’s jurisdictional reach is generally
broader than the RHA’s, the reversal here is explained by the
RHA’s concern with preventing obstructions, on the one
hand, and the CWA’s focus on discharges into water, on the
other. Since the two laws serve different purposes, their regu-
latory powers will diverge in some circumstances, as is the
case here. Under the RHA, it is appropriate to ignore an
obstruction’s ability to stop the flow of navigable water,
because the purpose of the RHA is precisely to prevent or
remove obstructions to navigable waters. The Homeowners’
structures clearly impinge on the capacity of the Strait of
Georgia and portions of them sit within navigable waters;
14492                UNITED STATES v. NICHOLSON
they are therefore obstructions. The CWA, on the other hand,
is designed to restore and maintain the integrity of the
nation’s waters, which it does by limiting the discharge of
pollutants into the waters. See 33 U.S.C. § 1251(a). The Nich-
olsons’ activities in reconstructing their bulkhead, however,
would not involve a discharge into waters of the United States
if conducted solely on fast land. The revetment fronting their
bulkhead may have prevented the MHHW line from reaching
the construction work—and thereby prevented a discharge
into navigable waters—while at the same time obstructing
those waters. It is perfectly consistent, then, that the Home-
owners could be liable under the RHA while the Nicholsons
may not be liable under the CWA.

                                   D.

   Finally, for the court to award attorney’s fees and costs
under the EAJA, it must be shown that (1) the party seeking
fees is the prevailing party; (2) the government has not met
its burden of showing that its positions were substantially jus-
tified or that special circumstances make an award unjust; and
(3) the requested fees and costs are reasonable. See Perez-
Arellano v. Smith, 279 F.3d 791, 793 (9th Cir. 2002).

   [25] To be a prevailing party, the party must have received
an enforceable judgment on the merits or a court-ordered con-
sent decree. Id.; see Buckhannon Bd. & Care Home, Inc. v. W.
Va. Dep’t of Health & Human Res., 532 U.S. 598, 604 (2001)
(“[E]nforceable judgments on the merits and court-ordered
consent decrees create the ‘material alteration of the legal
relationship of the parties’ necessary to permit an award of
attorney’s fees.” (citation omitted)). The Milners and Ben-
nett/Boyd stipulated to the government’s dismissal, without
prejudice,16 of the CWA claims against them. However,
although a defendant may no longer have a claim pending
  16
    Since the stipulation did not state that the dismissal was with preju-
dice, it was without prejudice. Fed. R. Civ. Proc. 41(a)(1)(B).
                  UNITED STATES v. NICHOLSON               14493
against him or her upon dismissal, a dismissal without preju-
dice does not materially alter the legal relationship of the par-
ties, because the defendant remains subject to the risk of re-
filing. Oscar v. Alaska Dep’t of Educ. & Early Dev., 541 F.3d
978, 981 (9th Cir. 2008); Cadkin v. Loose, 569 F.3d 1142,
1149 (9th Cir. 2009). Although Oscar and Cadkin concern
fee-shifting statutes other than the EAJA, they turn on the
meaning of the term “prevailing party” and govern our inter-
pretation here. See Perez-Arellano, 279 F.3d at 794 (noting
that Buckhannon “sweeps . . . broadly and its reasoning is per-
suasively applicable to an award of attorney’s fees under the
EAJA”); Oscar, 541 F.3d at 981 (relying on Buckhannon to
determine whether a defendant is a prevailing party); Cadkin,
569 F.3d at 1149 (same). We therefore conclude that the Mil-
ners and Bennett/Boyd are not prevailing parties and are not
entitled to attorneys’ fees under the EAJA.

                              IV.

   Although this particular dispute has been ongoing for some
years now, for an even longer period of time, the Homeown-
ers on Sandy Point had an agreement with the Lummi Nation
to lease the tidelands. This allowed the upland owners to con-
struct and maintain bulkheads, rip rap, and other shore
defense structures on the tidelands in order to protect their
property. The Sandy Point Homeowners had an opportunity to
renew the lease for an additional 25 years, the maximum lease
term allowed for Indian trust lands. 25 U.S.C. § 415. Addi-
tionally, throughout this litigation the Lummi have expressed
a desire to negotiate a new agreement, and at least before
commencement of this suit, the United States indicated that its
concerns would be satisfied if the Homeowners entered into
agreements with the Lummi.

   This action was avoidable. Perhaps the parties still will be
able to reach an amicable settlement. However, because the
Homeowners have so far been unable or unwilling to negoti-
ate an agreement with the Lummi, we must pass on the merits
14494            UNITED STATES v. NICHOLSON
of the dispute. For the reasons set forth above, we affirm the
district court’s decisions on the trespass and RHA claims, and
its decision not to grant fees under the EAJA. We find that the
government did not carry its burden on the CWA claim
against the Nicholsons; we therefore reverse on that claim.

  Each party is to bear its own costs on appeal.

 AFFIRMED IN PART, REVERSED IN PART, AND
REMANDED.
