                Certiorari dismissed, July 22, 2011




                        PUBLISHED


UNITED STATES COURT OF APPEALS
             FOR THE FOURTH CIRCUIT


STATE OF NORTH CAROLINA, ex rel.         
Roy Cooper, Attorney General,
                Plaintiff-Appellee,
               v.
TENNESSEE VALLEY AUTHORITY,
             Defendant-Appellant,
STATE OF ALABAMA,
                        Intervenor,


COMMONWEALTH OF KENTUCKY;
STATE OF LOUISIANA; STATE OF
NORTH DAKOTA; STATE OF SOUTH
DAKOTA; STATE OF UTAH; STATE OF                  No. 09-1623
WYOMING; GERARD V. BRADLEY;
RONALD A. CASS; JAMES L.
HUFFMAN; F. SCOTT KIEFF; JOHN J.
PARK, JR.; JIM COOPER,
Representative; PHIL ROE,
Representative; STEVE COHEN,
Representative; MARSHA
BLACKBURN, Representative;
LINCOLN DAVIS, Representative;
ZACH WAMP, Representative; BART
GORDON, Representative; JOHN
TANNER, Representative; PARKER
GRIFFITH, Representative; TRAVIS
CHILDERS, Representative;
CHAMBER OF COMMERCE OF THE
                                         
2               STATE OF NORTH CAROLINA v. TVA


UNITED STATES OF AMERICA;             
NATIONAL ASSOCIATION OF
MANUFACTURERS; AMERICAN
PETROLEUM INSTITUTE; PUBLIC
NUISANCE FAIRNESS COALITION;
UTILITY AIR REGULATORY GROUP;
AMERICAN FOREST AND PAPER
ASSOCIATION; STATE OF TENNESSEE,
       Amici Supporting Appellant,
ENVIRONMENTAL LAW PROFESSORS;
AMERICAN LUNG ASSOCIATION;
AMERICAN THORACIC SOCIETY;
NATIONAL PARKS CONSERVATION
ASSOCIATION; NATURAL RESOURCES
DEFENSE COUNCIL; SIERRA CLUB;
                                      
STATE OF CALIFORNIA; STATE OF
CONNECTICUT; STATE OF DELAWARE;
STATE OF ILLINOIS; STATE OF IOWA;
STATE OF MAINE; STATE OF
MARYLAND; STATE OF
MASSACHUSETTS; STATE OF
MISSISSIPPI; STATE OF NEW
HAMPSHIRE; STATE OF NEW JERSEY;
STATE OF NEW MEXICO; STATE OF
NEW YORK; STATE OF OKLAHOMA;
STATE OF RHODE ISLAND; STATE OF
VERMONT,
        Amici Supporting Appellee.
                                      
          Appeal from the United States District Court
    for the Western District of North Carolina, at Asheville.
              Lacy H. Thornburg, District Judge.
                     (1:06-cv-00020-LHT)
              STATE OF NORTH CAROLINA v. TVA              3
                  Argued: May 14, 2010

                  Decided: July 26, 2010

     Before WILKINSON, NIEMEYER and SHEDD,
                   Circuit Judges.



Reversed and remanded by published opinion. Judge Wilkin-
son wrote the opinion, in which Judge Niemeyer and Judge
Shedd joined.


                        COUNSEL

ARGUED: Harriet A. Cooper, TENNESSEE VALLEY
AUTHORITY, Knoxville, Tennessee, for Appellant. Kevin
Christopher Newsom, BRADLEY ARANT BOULT CUM-
MINGS, LLP, Birmingham, Alabama, for Intervenor. Chris-
topher Grafflin Browning, Jr., NORTH CAROLINA
DEPARTMENT OF JUSTICE, Raleigh, North Carolina, for
Appellee. ON BRIEF: F. William Brownell, Makram B.
Jaber, David J. DePippo, HUNTON & WILLIAMS LLP,
Washington, D.C.; Maureen H. Dunn, General Counsel,
Frank H. Lancaster, Senior Attorney, Maria V. Gillen, Office
of the General Counsel, TENNESSEE VALLEY AUTHOR-
ITY, Knoxville, Tennessee, for Appellant. Michael D. Good-
stein, Stacey H. Myers, Anne E. Lynch, HUNSUCKER
GOODSTEIN & NELSON P.C., Washington, D.C.; Richard
E. Ayres, AYRES LAW GROUP, Washington, D.C.; James
C. Gulick, Senior Deputy Attorney General, Marc Bernstein,
Special Deputy Attorney General, NORTH CAROLINA
DEPARTMENT OF JUSTICE, Raleigh, North Carolina, for
Appellee. Troy King, Attorney General, Corey Maze, Solici-
tor General, William G. Parker, Jr., Assistant Attorney Gen-
eral, STATE OF ALABAMA, OFFICE OF THE
4             STATE OF NORTH CAROLINA v. TVA
ATTORNEY GENERAL, Montgomery, Alabama; Brian M.
Vines, BRADLEY ARANT BOULT CUMMINGS, LLP, Bir-
mingham, Alabama, for Intervenor. Jack Conway, Attorney
General, Tad Thomas, Assistant Deputy Attorney General,
COMMONWEALTH OF KENTUCKY, OFFICE OF THE
ATTORNEY GENERAL, Frankfort, Kentucky, for the Com-
monwealth of Kentucky; James D. "Buddy" Caldwell, Attor-
ney General, STATE OF LOUISIANA, OFFICE OF THE
ATTORNEY GENERAL, Baton Rouge, Louisiana, for the
State of Louisiana; Wayne Stenehjem, Attorney General,
STATE OF NORTH DAKOTA, OFFICE OF THE ATTOR-
NEY GENERAL, Bismarck, North Dakota, for the State of
North Dakota; Lawrence E. Long, Attorney General, Roxanne
Giedd, Assistant Attorney General, STATE OF SOUTH
DAKOTA, OFFICE OF THE ATTORNEY GENERAL,
Pierre, South Dakota, for the State of South Dakota; Mark L.
Shurtleff, Attorney General, STATE OF UTAH, OFFICE OF
THE ATTORNEY GENERAL, Salt Lake City, Utah, for the
State of Utah; Bruce A. Salzburg, STATE OF WYOMING,
OFFICE OF THE ATTORNEY GENERAL, Cheyenne, Wyo-
ming, for the State of Wyoming, Amici Supporting Appellant.
David B. Rivkin, Jr., Lee A. Casey, Mark W. DeLaquil,
BAKER & HOSTETLER LLP, Washington, D.C., for Gerard
V. Bradley, Ronald A. Cass, James L. Huffman, F. Scott
Kieff, and John J. Park, Jr., Amici Supporting Appellant. Erik
S. Jaffe, ERIK S. JAFFE, P.C., Washington, D.C.; C. Boyden
Gray, Washington, D.C., for Jim Cooper, Phil Roe, Steve
Cohen, Marsha Blackburn, Lincoln Davis, Zach Wamp, Bart
Gordon, John Tanner, Parker Griffith, and Travis Childers,
Amici Supporting Appellant. Charles H. Knauss, Michael B.
Wigmore, Robert V. Zener, Sandra P. Franco, BINGHAM
MCCUTCHEN LLP, Washington, D.C., for Chamber of
Commerce of the United States of America, National Associ-
ation of Manufacturers, American Petroleum Institute, Public
Nuisance Fairness Coalition, Utility Air Regulatory Group,
and American Forest and Paper Association; William L.
Wehrum, HUNTON & WILLIAMS, Washington, D.C., for
              STATE OF NORTH CAROLINA v. TVA              5
the Utility Air Regulatory Group; Quentin Riegel,
NATIONAL ASSOCIATION OF MANUFACTURERS,
Washington, D.C.; George S. Kopp, PUBLIC NUISANCE
FAIRNESS COALITION, Washington, D.C.; Robin S. Con-
rad, Amar D. Sarwal, NATIONAL CHAMBER LITIGA-
TION CENTER, INC., for the Chamber of Commerce of the
United States; Harry M. Ng, Stacy R. Linden, Office of the
General Counsel, AMERICAN PETROLEUM INSTITUTE,
Washington, D.C., Jan Poling, Vice President, General Coun-
sel & Corporate Secretary, AMERICAN FOREST & PAPER
ASSOCIATION, Washington, D.C., for Amici Supporting
Appellant. Robert E. Cooper, Jr., Attorney General and
Reporter, Barry Turner, Deputy Attorney General, OFFICE
OF THE TENNESSEE ATTORNEY GENERAL AND
REPORTER, Nashville, Tennessee, for the State of Tennes-
see, Amicus Supporting Appellant and Intervenor. Patrick
Parenteau, VERMONT LAW SCHOOL, Environmental and
Natural Resources Law Clinic, South Royalton, Vermont, for
Environmental Law Professors, Amicus Supporting Appellee.
Jamie Gibbs Pleune, Staff Attorney, Hope M. Babcock,
Senior Attorney/Director, GEORGETOWN UNIVERSITY
LAW CENTER, Institute for Public Representation, Wash-
ington, D.C., for American Lung Association and American
Thoracic Society, Amici Supporting Appellee. John T. Sut-
tles, Jr., SOUTHERN ENVIRONMENTAL LAW CENTER,
Chapel Hill, North Carolina, for National Parks Conservation
Association, Natural Resources Defense Council, and Sierra
Club, Amici Supporting Appellee; Mitchell S. Bernard, NAT-
URAL RESOURCES DEFENSE COUNCIL, New York,
New York, for Natural Resources Defense Council, Amicus
Supporting Appellee; Jamie Gibbs Pleune, Hope M. Babcock,
GEORGETOWN UNIVERSITY LAW CENTER, Institute
for Public Representation, Washington, D.C., for National
Parks Conservation Association, Natural Resources Defense
Council, and Sierra Club, Amici Supporting Appellee.
Andrew M. Cuomo, Attorney General, Barbara D. Under-
wood, Solicitor General, Katherine Kennedy, Special Deputy
6              STATE OF NORTH CAROLINA v. TVA
Attorney General, Robert Rosenthal, Assistant Attorney Gen-
eral, Monica Wagner, Assistant Solicitor General, STATE OF
NEW YORK, Office of the Attorney General, New York,
New York; Douglas F. Gansler, Attorney General, Steven M.
Sullivan, Solicitor General, William F. Brockman, Deputy
Solicitor General, STATE OF MARYLAND, Office of the
Attorney General, Baltimore, Maryland, for States of Califor-
nia, Connecticut, Delaware, Illinois, Iowa, Maine, Maryland,
Massachusetts, Mississippi, New Hampshire, New Jersey,
New Mexico, New York, Oklahoma, Rhode Island, and Ver-
mont, Amici Supporting Appellee.


                          OPINION

WILKINSON, Circuit Judge:

   The Tennessee Valley Authority (TVA) appeals an injunc-
tion requiring immediate installation of emissions controls at
four TVA electricity generating plants in Alabama and Ten-
nessee. The injunction was based on the district court’s deter-
mination that the TVA plants’ emissions constitute a public
nuisance in North Carolina. As a result, the court imposed
specific emissions caps and emissions control technologies
that must be completed by 2013.

   This ruling was flawed for several reasons. If allowed to
stand, the injunction would encourage courts to use vague
public nuisance standards to scuttle the nation’s carefully cre-
ated system for accommodating the need for energy produc-
tion and the need for clean air. The result would be a
balkanization of clean air regulations and a confused patch-
work of standards, to the detriment of industry and the envi-
ronment alike. Moreover, the injunction improperly applied
home state law extraterritorially, in direct contradiction to the
Supreme Court’s decision in International Paper Co. v. Ouel-
lette, 479 U.S. 481 (1987). Finally, even if it could be
               STATE OF NORTH CAROLINA v. TVA                  7
assumed that the North Carolina district court did apply Ala-
bama and Tennessee law, it is difficult to understand how an
activity expressly permitted and extensively regulated by both
federal and state government could somehow constitute a
public nuisance. For these reasons, the judgment must be
reversed.

                               I.

   The Tennessee Valley Authority (TVA) is a federal execu-
tive branch agency, established in 1933 and tasked with pro-
moting economic development in the Tennessee Valley
region. 48 Stat. 58 (May 18, 1933). One of TVA’s "primary
objectives" is to "produce, distribute, and sell electric power."
16 U.S.C. §§ 831d(l), 831i, & 831n-4(f). As a result of this
mandate, TVA provides electricity to citizens in parts of
seven states. Much of this power is generated by eleven TVA
owned and operated coal-fired power plants located in Ten-
nessee, Alabama, and Kentucky.

   As a natural byproduct of the power generation process,
coal-fired power plants emit sulfur dioxide (SO2) and nitrous
oxides (NOx). In the atmosphere, both compounds can trans-
form into microscopic particles known as "fine particulate
matter" or "PM2.5" (particulate matter less than 2.5 microme-
ters in diameter) that cause health problems if inhaled. When
exposed to sunlight, NOx also assists in the creation of ozone,
which is known to cause respiratory ailments.

   SO2, NOx, PM2.5, and ozone are among the air pollutants
extensively regulated through the Clean Air Act, 42 U.S.C.
§ 7401 et seq. Pursuant to the Act, the Environmental Protec-
tion Agency (EPA) has issued numerous regulations, and
states have enacted further rules implementing the Act and the
EPA requirements. Together, these laws and regulations form
a system that seeks to keep air pollutants at or below safe
levels.
8              STATE OF NORTH CAROLINA v. TVA
   In order to comply with requirements under the Clean Air
Act, a number of controls can be fitted to coal-fired power
plants to reduce the amounts of SO2 and NOx they emit and,
by extension, the amounts of PM2.5 and ozone created. One of
the ways SO2 can be reduced, for example, is by installing a
flue gas desulfurization system, or "scrubber." Scrubbers are
large chemical plants—often larger than the power plants
themselves—that remove SO2—from plant exhaust and cost
hundreds of millions of dollars.

   To control NOx emissions, plants may use selective cata-
lytic reduction (SCR). Like scrubbers, SCRs are building-
sized plants that can cost hundreds of millions of dollars to
construct. However, they can remove approximately 90% of
the NOx from the flue gasses a coal power plant produces. NOx
emissions can also be reduced in alternative ways, such as
retrofitting plants with burners that result in lower NOx emis-
sions, burning types of coal that have low NOx output, and
installing selective non-catalytic reduction (SNCR) controls.
Although SNCRs are not as effective as SCRs, removing
some 20 to 40% of NOx, they have the benefit of costing
about one-tenth as much as SCRs.

   TVA has already installed numerous pollution controls at
its coal-fired plants. SO2 scrubbers already operating cover
43% of TVA’s coal-fired electricity generation capacity,
while scrubbers under construction and anticipated to be com-
pleted this year will bring that number above 50%. Nation-
wide, only one-third to one-half of the country’s coal plants
are equipped with scrubbers. Similarly, while one-third to
one-half of the country’s coal plants have SCRs to control
NOx, TVA has installed SCRs on 60% of its coal-fired elec-
tricity generation capacity. At several plants that do not cur-
rently have SCRs, TVA is installing SNCRs and is also
burning low NOx coal.

  Unlike TVA, power plants in North Carolina historically
had not put sufficient controls on their emissions, choosing
               STATE OF NORTH CAROLINA v. TVA                 9
instead to purchase emissions allowances under an EPA cap
and trade program implemented by Congress in 1990 to
address acid rain. See 42 U.S.C. § 7651-7651o (Clean Air Act
Title IV, Acid Deposition Control); 42 U.S.C. § 7651b(b)
(emissions allowance transfer system under acid rain pro-
gram). As a result, North Carolina decided to implement more
stringent controls on in-state coal-fired plants as a matter of
state law, as it is allowed to do under the Clean Air Act. See
42 U.S.C. § 7416. It passed the North Carolina Clean Smoke-
stacks Act, N.C. Gen. Stat. § 143-215.107D, which requires
investor-owned public utilities that operate coal-fired generat-
ing units to reduce their emissions of NOx and SO2 to levels
even lower than those specified in EPA regulations promul-
gated pursuant to the Clean Air Act. N.C. Gen. Stat. § 143-
215.107D(b)-(e).

   Not all emissions are generated by in-state sources, how-
ever. Prevailing high pressure weather systems in the states
where TVA operates tend to cause emissions to move east-
ward into North Carolina and other states. North Carolina v.
Tenn. Valley Auth., 593 F. Supp. 2d 812, 825 (W.D.N.C.
2009). Although there are lengthy Clean Air Act provisions
and regulations controlling such interstate emissions, North
Carolina chose to bring a public nuisance suit against TVA in
the Western District of North Carolina, seeking an injunction
against all eleven of TVA’s coal-fired power plants. TVA
moved to dismiss based on the discretionary function doctrine
and the Supremacy Clause. The district court denied the
motions. North Carolina v. Tenn. Valley Auth., 439 F. Supp.
2d 486 (W.D.N.C. 2006). We affirmed, holding that TVA’s
immunity was waived because the Clean Air Act required
federal entities to comply with state and local regulations "in
the same manner, and to the same extent as any nongovern-
mental entity," 42 U.S.C. § 7418(a), and because Congress
provided that TVA may "sue and be sued in its corporate
name," 16 U.S.C. § 831c(b). North Carolina v. Tenn. Valley
Auth., 515 F.3d 344 (4th Cir. 2008) (TVA I).
10             STATE OF NORTH CAROLINA v. TVA
   Upon resolution of the interlocutory appeal, the district
court held a bench trial, North Carolina v. Tenn. Valley Auth.,
593 F. Supp. 2d at 818, at the end of which it issued an
injunction against four of the power plants. All of these plants
were within 100 miles of the North Carolina border. The
injunction required TVA to install and continuously operate
scrubbers and SCRs at each of the plants by December 31,
2013. Id. at 832. In addition to these requirements, the district
court also established a schedule of SO2 and NOx emissions
limits for each electric generation unit at the four plants, cap-
ping the emissions that each unit was allowed to release. Id.
at 832-33. Primarily because TVA’s seven other plants are
located farther from North Carolina, the district court con-
cluded there was insufficient evidence that they contributed
significantly to pollution in North Carolina. Id. at 831-32. As
a result, it did not rule that they were a public nuisance.

   The cost of compliance with the district court’s injunction
against the four TVA plants is uncertain, but even North Car-
olina admits it will be over a billion dollars, while TVA esti-
mates that the actual cost will be even higher. Regardless of
the actual amount, there is no question that costs will be
passed on in the form of rate increases to citizens who pur-
chase power from TVA. TVA appealed the injunctions
against its four plants, and we granted leave to the state of
Alabama to intervene on appeal on TVA’s behalf.

                               II.

   The desirability of reducing air pollution is widely
acknowledged, but the most effective means of doing so
remains, not surprisingly, a matter of dispute. The system of
statutes and regulations addressing the problem represents
decades of thought by legislative bodies and agencies and the
vast array of interests seeking to press upon them a variety of
air pollution policies. To say this regulatory and permitting
regime is comprehensive would be an understatement. To say
it embodies carefully wrought compromises states the obvi-
                STATE OF NORTH CAROLINA v. TVA                  11
ous. But the framework is the work of many, many people,
and it is in place.

   The district court’s well-meaning attempt to reduce air pol-
lution cannot alter the fact that its decision threatens to scuttle
the extensive system of anti-pollution mandates that promote
clean air in this country. If courts across the nation were to
use the vagaries of public nuisance doctrine to overturn the
carefully enacted rules governing airborne emissions, it would
be increasingly difficult for anyone to determine what stan-
dards govern. Energy policy cannot be set, and the environ-
ment cannot prosper, in this way.

                                A.

   North Carolina attempts to frame this case in terms of pro-
tecting public health and saving the environment from dirty
air. But the problem is not a neglected one. In fact, emissions
have been extensively regulated nationwide by the Clean Air
Act for four decades. The real question in this case is whether
individual states will be allowed to supplant the cooperative
federal-state framework that Congress through the EPA has
refined over many years.

   It is worth describing this system in some detail. The fed-
eral Clean Air Act, 42 U.S.C. § 7401 et seq., is the primary
mechanism under which emissions in the United States are
managed. The Act makes the EPA responsible for developing
acceptable levels of airborne emissions, known as National
Ambient Air Quality Standards (NAAQS), "the attainment
and maintenance of which . . . are requisite to protect the pub-
lic health." 42 U.S.C. § 7409(b)(1). NAAQS are further sub-
divided into Primary NAAQS, 42 U.S.C. § 7409(b)(1), and
Secondary NAAQS, 42 U.S.C. § 7409(b)(2). Primary
NAAQS are intended to protect individuals, while Secondary
NAAQS are set to protect the surrounding environment. In
practice, the two standards are often, though not necessarily,
the same. See 40 C.F.R. § 50. As the name suggests, NAAQS
12             STATE OF NORTH CAROLINA v. TVA
are meant to set a uniform level of air quality across the coun-
try in order to guarantee both a healthy populace and a
healthy environment. See Her Majesty the Queen v. City of
Detroit, 874 F.2d 332, 335 (6th Cir. 1989).

   As a result of this statutory directive, the EPA has promul-
gated NAAQS for a number of emissions, including standards
for all of the emissions involved in this case. See 40 C.F.R.
§§ 50.4 & 50.5 (SO2), 50.9 & 50.15 (ozone), 50.11 (NOx), &
50.13 (PM2.5). For instance, the NAAQS level for PM2.5 across
the country is set at an annual average of fifteen micrograms
per cubic meter (15 µg/m3) and at thirty-five micrograms per
cubic meter (35 µg/m3) for a twenty-four hour period. 40
C.F.R. § 50.13. Such standards, however, are not set arbitrar-
ily by the EPA. Rather, "a reasonable time for interested per-
sons to submit written comments" must be provided before
NAAQS may be adopted or modified. 42 U.S.C.
§ 7409(a)(1)(B), (b)(1) & (2). The EPA also has adopted
extensive regulations explaining proper scientific equipment
and techniques and providing detailed schematic diagrams for
measuring emissions levels and air quality, see 40 C.F.R.
§ 50, apps. A-R, to ensure that measurements will be consis-
tent across the country.

                               B.

   While it establishes acceptable nationwide emissions
levels, however, the EPA does not directly regulate actual
sources of emissions. In light of the fact that Congress recog-
nized "that air pollution prevention . . . and air pollution con-
trol at its source is the primary responsibility of States and
local governments," 42 U.S.C. § 7401(a)(3), decisions regard-
ing how to meet NAAQS are left to individual states. 42
U.S.C. § 7410(a)(1). Pursuant to this goal, each state is
required to create and submit to the EPA a State Implementa-
tion Plan (SIP) "which provides for implementation, mainte-
nance, and enforcement of [NAAQS] . . . within such State."
Id. While states are responsible for promulgating SIPs, they
               STATE OF NORTH CAROLINA v. TVA                  13
must do so consistently with extensive EPA regulations gov-
erning preparation, adoption by the state, and submission to
the EPA, 40 C.F.R. § 51, and all SIPs must be submitted to
the EPA for approval before they become final. 42 U.S.C.
§ 7410(a)(1), (k)(2) & (3). Once a SIP is approved, however,
"its requirements become federal law and are fully enforce-
able in federal court." Her Majesty the Queen, 874 F.2d at
335 (citing 42 U.S.C. § 7604(a)).

   States are accorded flexibility in determining how their
SIPs are structured, but regardless of their choices, SIPs must
"include enforceable emission limitations and other control
measures, means, or techniques" to ensure that each state
meets NAAQS. 42 U.S.C. § 7410(a)(2)(A). States are also
tasked with enforcing the limitations they adopt in their SIPs.
They must regulate "the modification and construction of any
stationary source within the areas covered by the [SIP]," 42
U.S.C. § 7410(a)(2)(C), and must implement a permit pro-
gram that limits the amounts and types of emissions that each
permit holder is allowed to discharge, 42 U.S.C.
§§ 7661a(d)(1), 7661c(a). Sources are prohibited from operat-
ing without such a permit, 42 U.S.C. § 7661a(a), and each
permit is intended to be "a source-specific bible for Clean Air
Act compliance" containing "in a single, comprehensive set of
documents, all CAA requirements relevant to the particular
polluting source." Virginia v. Browner, 80 F.3d 869, 873 (4th
Cir. 1996).

    Critically for this case, each SIP must consider the impact
of emissions within the state on the ability of other states to
meet NAAQS. The Clean Air Act requires each state to
ensure that its SIP "contain[s] adequate provisions prohibiting
. . . any source . . . within the State from emitting any air pol-
lutant in amounts which will contribute significantly to nonat-
tainment in, or interfere with maintenance by, any other State
with respect to any such national primary or secondary ambi-
ent air quality standard." 42 U.S.C. § 7410(a)(2)(D), (D)(i), &
(D)(i)(I) (internal section breaks omitted). This rule prevents
14             STATE OF NORTH CAROLINA v. TVA
states from essentially exporting most of their emissions to
other regions by strategically positioning sources along an
arbitrary border line.

   In addition, before new construction or modifications of a
source of emissions may begin, a SIP must provide for "writ-
ten notice to all nearby States the air pollution levels of which
may be affected by such source at least sixty days prior to the
date on which commencement of construction is to be permit-
ted." 42 U.S.C. § 7426(a)(1).

   Both Alabama and Tennessee have promulgated SIPs, and
as part of its compliance with these regulations TVA has
sought and obtained state permits to operate each of its power
plants. As far as the record before us indicates, TVA currently
operates each of the four plants at issue in this case in confor-
mity with the permits, including limitations on SO2 and NOx
emissions. Indeed, this suit does not present a challenge to
Alabama and Tennessee’s SIPs, the permits issued to TVA
pursuant to them, or TVA’s operation pursuant to the permits.

   In addition to this framework, there are a number of checks
built into the system to prevent abuses and to address con-
cerns about emissions. As already noted, the EPA retains ulti-
mate authority over NAAQS to determine what levels of
emissions are acceptable and has the responsibility to modify
those levels as necessary. 42 U.S.C. § 7409(b)(1) & (2). The
EPA also has the authority, through a procedure known as a
SIP Call, to demand that states modify their SIPs if it believes
they are inadequate to meet NAAQS. 42 U.S.C. § 7410(k)(5).
Finally, any state that believes that it is being subjected to
interstate emissions may file what is known as a section 126
petition. Named after the original section of the Clean Air Act
and codified at 42 U.S.C. § 7426(b), the section states that
"[a]ny State or political subdivision may petition the Admin-
istrator [of the EPA] for a finding that any major source or
group of stationary sources emits or would emit any air pollu-
tant in violation of the prohibition of section
                  STATE OF NORTH CAROLINA v. TVA                           15
7410(a)(2)(D)([i]) of this title or this section."1 42 U.S.C.
§ 7426(b). As noted earlier, section 7410(a)(2)(D)(i)(I) pro-
hibits states from allowing emissions that will interfere with
other states’ attainment or maintenance of NAAQS air emis-
sion levels. Thus, section 126 provides an important method
for downwind states like North Carolina to address any con-
cerns they have regarding the adequacy of an upwind state’s
regulation of airborne emissions.

                                     III.

   We have explained at some length the structure of the
Clean Air Act in order to emphasize the comprehensiveness
of its coverage. The fact that the process has been regulated
in such detail has contributed to its inclusiveness and predict-
ability. It was hardly unforeseeable that the aforementioned
process and the plans and permits related to it would not meet
with universal approbation. Litigation that amounts to "noth-
ing more than a collateral attack" on the system, however,
risks results that lack both clarity and legitimacy. Palumbo v.
Waste Techs. Indus., 989 F.2d 156, 159 (4th Cir. 1993).

    Dissatisfied with the air quality standards authorized by
Congress, established by the EPA, and implemented through
Alabama and Tennessee permits, North Carolina has
requested the federal courts to impose a different set of stan-
dards. The pitfalls of such an approach are all too evident. It
ill behooves the judiciary to set aside a congressionally sanc-
tioned scheme of many years’ duration—a scheme, moreover,
that reflects the extensive application of scientific expertise
  1
    Section 126’s cross reference contains an apparent scrivener’s error as
a result of renumbering during extensive amendments in 1990. The section
as printed references section 7410(a)(2)(D)(ii), but section 126(b) prior to
amendment referenced what is now section 7410(a)(2)(D)(i). The EPA
"contends that the Congress amended § 126 only in order to update the
cross-references" and that this "substitution of ‘(ii)’ for ‘(i)’ was inadver-
tent." Appalachian Power Co. v. EPA, 249 F.3d 1032, 1040 (D.C. Cir.
2001) (citation omitted).
16             STATE OF NORTH CAROLINA v. TVA
and that has set in motion reliance interests and expectations
on the part of those states and enterprises that have complied
with its requirements. To replace duly promulgated ambient
air quality standards with standards whose content must await
the uncertain twists and turns of litigation will leave whole
states and industries at sea and potentially expose them to a
welter of conflicting court orders across the country.

                               A.

   The Supreme Court addressed this precise problem of mul-
tiplicity in International Paper Co. v. Ouellette, 479 U.S. 481
(1987). It emphasized that allowing "a number of different
states to have independent and plenary regulatory authority
over a single discharge would lead to chaotic confrontation
between sovereign states." Id. at 496-97 (quoting Illinois v.
City of Milwaukee, 731 F.2d 403, 414 (7th Cir. 1984)). This
problem is only exacerbated if state nuisance law is the mech-
anism used, because "nuisance standards often are vague and
indeterminate." Id. at 496 (citation omitted).

   Indeed, the district court properly recognized that "[t]he
ancient common law of public nuisance is not ordinarily the
means by which such major conflicts among governmental
entities are resolved in modern American governance." North
Carolina v. Tenn. Valley Auth., 593 F. Supp. 2d at 815. This
is at least in part because public nuisance is an all-purpose tort
that encompasses a truly eclectic range of activities. It
includes such broad-ranging offenses as:

     interferences with the public health, as in the case of
     a hogpen, the keeping of diseased animals, or a
     malarial pond; with the public safety, as in the case
     of the storage of explosives, the shooting of fire-
     works in the streets, harboring a vicious dog, or the
     practice of medicine by one not qualified; with pub-
     lic morals, as in the case of houses of prostitution,
     illegal liquor establishments, gambling houses, inde-
               STATE OF NORTH CAROLINA v. TVA                 17
    cent 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 com-
    fort, 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 condi-
    tion which makes travel unsafe or highly disagree-
    able, or the collection of an inconvenient crowd; and
    in addition, such unclassified offenses as eavesdrop-
    ping on a jury, or being a common scold.

W. Page Keeton et al., Prosser and Keeton on the Law of
Torts 643-45 (5th ed. 1984) (citing numerous examples). See
also Restatement (Second) of Torts § 821B cmts. b & c; Com-
monwealth Edison Co. v. United States, 271 F.3d 1327, 1353
(Fed. Cir. 2001) (en banc) ("When discussing the contours
and scope of the common law, the Supreme Court has
instructed that it is appropriate for us to look to the pertinent
Restatement and other secondary sources.") (citing cases and
Restatement (Second) of Torts).

   Thus, while public nuisance law doubtless encompasses
environmental concerns, it does so at such a level of general-
ity as to provide almost no standard of application. If we are
to regulate smokestack emissions by the same principles we
use to regulate prostitution, obstacles in highways, and bull-
fights, see Keeton, supra, at 643-45, we will be hard pressed
to derive any manageable criteria. As Justice Blackmun com-
mented, "one searches in vain . . . for anything resembling a
principle in the common law of nuisance." Lucas v. S.C.
Coastal Council, 505 U.S. 1003, 1055 (1992) (Blackmun, J.,
dissenting).

  The contrast between the defined standards of the Clean
Air Act and an ill-defined omnibus tort of last resort could not
be more stark. We are hardly at liberty to ignore the Supreme
Court’s concerns and the practical effects of having multiple
18              STATE OF NORTH CAROLINA v. TVA
and conflicting standards to guide emissions. These difficul-
ties are heightened if we allow multiple courts in different
states to determine whether a single source constitutes a nui-
sance. "Adding another layer of collateral review for agency
decisions threatens to put at naught the . . . process established
by Congress." Palumbo, 989 F.2d at 161. An EPA-sanctioned
state permit may set one standard, a judge in a nearby state
another, and a judge in another state a third. Which standard
is the hapless source to follow? See Ouellette, 479 U.S. at 496
n.17.

   Indeed, a patchwork of nuisance injunctions could well
lead to increased air pollution. Differing standards could
create perverse incentives for power companies to increase
utilization of plants in regions subject to less stringent judicial
decrees. Alabama Br. at 62. Similarly, rushed plant alterations
triggered by injunctions are likely inferior to system-wide
analysis of where changes will do the most good. Injunction-
driven demand for such artificial changes could channel a
limited pool of specialized construction expertise away from
the plants most in need of pollution controls to those with the
most pressing legal demands. Tennessee Br. at 8-9, 12. Even
these scenarios probably fail to exhaust the full scope of
unpredictable consequences and potential confusion. "It is
unlikely—to say the least—that Congress intended to estab-
lish such a chaotic regulatory structure." Ouellette, 479 U.S.
at 497.

                                B.

  We need not hold flatly that Congress has entirely pre-
empted the field of emissions regulation. See Pac. Gas &
Elec. Co. v. State Energy Res. Conservation & Dev. Comm.,
461 U.S. 190, 203-04 (1983). We cannot anticipate every cir-
cumstance that may arise in every future nuisance action. In
TVA I, for example, we held that the savings clause of the
Clean Air Act may allow for some common law nuisance
suits, although we did not address whether a nuisance action
               STATE OF NORTH CAROLINA v. TVA                  19
brought under these circumstances is barred by preemption
under the Supremacy Clause. The Ouellette Court itself
explicitly refrained from categorically preempting every nui-
sance action brought under source state law. 479 U.S. at 497-
99. At the same time, however, the Ouellette Court was
emphatic that a state law is preempted "if it interferes with the
methods by which the federal statute was designed to reach
[its] goal," id. at 494, admonished against the "tolerat[ion]" of
"common-law suits that have the potential to undermine [the]
regulatory structure," id. at 497, and singled out nuisance
standards in particular as "vague" and "indeterminate," id. at
496 (quoting City of Milwaukee v. Illinois, 451 U.S. 304, 317
(1981)) (internal quotation marks omitted). The upshot of all
this is that we cannot state categorically that the Ouellette
Court intended a flat-out preemption of each and every con-
ceivable suit under nuisance law. We can state, however, with
assurance that Ouellette recognized the considerable potential
mischief in those nuisance actions seeking to establish emis-
sions standards different from federal and state regulatory law
and created the strongest cautionary presumption against
them.

    In particular, it is essential that we respect the system that
Congress, the EPA, and the states have collectively estab-
lished. This is especially so in light of the fact that "‘the pur-
pose of Congress is the ultimate touchstone in every pre-
emption case.’" Wyeth v. Levine, 555 U.S. ___, 129 S.Ct.
1187, 1194 (2009) (quoting Medtronic, Inc. v. Lohr, 518 U.S.
470, 485 (1996)). A field of state law, here public nuisance
law, would be preempted if "a scheme of federal regulation
. . . [is] so pervasive as to make reasonable the inference that
Congress left no room for the States to supplement it." Pac.
Gas & Elec. Co., 461 U.S. at 204 (ellipsis in original, citation
omitted). Here, of course, the role envisioned for the states
has been made clear. Where Congress has chosen to grant
states an extensive role in the Clean Air Act’s regulatory
regime through the SIP and permitting process, field and con-
flict preemption principles caution at a minimum against
20             STATE OF NORTH CAROLINA v. TVA
according states a wholly different role and allowing state
nuisance law to contradict joint federal-state rules so meticu-
lously drafted.

   It is true, as North Carolina argues, that the Clean Air Act’s
savings clause states that "[n]othing in this section shall
restrict any right which any person (or class of persons) may
have under any statute or common law to seek enforcement
of any emission standard or limitation or to seek any other
relief." 42 U.S.C. § 7604(e). We must weigh that admonition,
however, in light of the Supreme Court’s direction in Pacific
Gas & Electric, 461 U.S. at 203-13. There the Court
explained that when Congress chose to give the Nuclear Reg-
ulatory Commission (at the time of the legislation the Atomic
Energy Commission) control over issues relating to nuclear
safety, it completely occupied the field of nuclear safety regu-
lations, notwithstanding a general savings clause indicating
that states retained their traditional power to regulate electri-
cal utilities. Id. at 210. As a result, the State of California’s
claim that "a State may completely prohibit new construction
until its safety concerns are satisfied by the Federal Govern-
ment" was rejected. Id. at 212. The Court explained that
"[w]hen the Federal Government completely occupies a given
field or an identifiable portion of it, . . . the test of pre-
emption is whether ‘the matter on which the State asserts the
right to act is in any way regulated by the Federal Act.’" Id.
at 212-13 (quoting Rice v. Santa Fe Elevator Corp., 331 U.S.
218, 236 (1947)). While the Court recognized that California
retained the right to regulate for traditional utilities purposes,
the case at bar mirrors Pacific Gas & Electric insofar as it
involves an attempt to replace comprehensive federal emis-
sions regulations with a contrasting state perspective about the
emission levels necessary to achieve those same public ends.

  Similarly, Ouellette held that the Clean Water Act’s sav-
ings clause, which is similar to the one found in the Clean Air
Act, compare 33 U.S.C. § 1365(e) with 42 U.S.C. § 7604(e),
did not preserve a broad right for states to "undermine this
               STATE OF NORTH CAROLINA v. TVA                21
carefully drawn statute through a general savings clause."
Ouellette, 479 U.S. at 494. The Court indicated that the clause
was ambiguous as to which state actions were preserved and
noted that "if affected States were allowed to impose separate
discharge standards on a single point source, the inevitable
result would be a serious interference with the achievement of
the ‘full purposes and objectives of Congress.’" Id. at 493-94
(quoting Hillsborough County v. Automated Med. Labs., Inc.,
471 U.S. 707, 713 (1985)). We thus cannot allow non-source
states to ascribe to a generic savings clause a meaning that the
Supreme Court in Ouellette held Congress never intended.

                              C.

   The difficulties with North Carolina’s approach in this liti-
gation do not end with the prospect of multiplicitous decrees
or vague and uncertain nuisance standards. In addition to
envisioning a role for the states that the Clean Air Act did not
contemplate, North Carolina’s approach would reorder the
respective functions of courts and agencies.

   One can, of course, debate the respective merits of agency
and judicial roles in addressing the problem of air pollution.
But Congress in the Clean Air Act opted rather emphatically
for the benefits of agency expertise in setting standards of
emissions controls, especially in comparison with the judi-
cially managed nuisance decrees for which North Carolina
argues. Indeed, the Act directs the EPA to ensure that its air
quality standards "accurately reflect the latest scientific
knowledge useful in indicating the kind and extent of all iden-
tifiable effects on public health or welfare which may be
expected from the presence of such pollutant in the ambient
air." 42 U.S.C. § 7408(a)(2). The Clean Air Act’s extensive
coverage allows regulators with expertise in the relevant sci-
entific fields to use their knowledge to create empirically-
based emissions standards. The Act even requires the EPA to
develop expertise so that it can provide states with informa-
tion about available emissions controls, including "cost of
22             STATE OF NORTH CAROLINA v. TVA
installation and operation, energy requirements, emission
reduction benefits, and environmental impact of the emission
control technology" as well as "data on alternative fuels, pro-
cesses, and operating methods which will result in elimination
or significant reduction of emissions." 42 U.S.C.
§ 7408(b)(1).

   One can argue whether expert witnesses in bench trials can
replicate the resources that EPA can bring to bear in deciding
appropriate emissions standards. But Congress evidently
thought not. It was certainly open to the legislative branch to
authorize various private causes of action as the primary
means of arriving at emissions standards. Congress, however,
thought the problem required a very high degree of special-
ized knowledge in chemistry, medicine, meteorology, biol-
ogy, engineering, and other relevant fields that agencies rather
than courts were likely to possess. "Congress has entrusted
the Agency with the responsibility for making these scientific
and other judgments, and we must respect both Congress’
decision and the Agency’s ability to rely on the expertise that
it develops." Lead Indus. Ass’n, Inc. v. EPA, 647 F.2d 1130,
1146 (D.C. Cir. 1980). See also id. ("We must look at the
decision not as the chemist, biologist, or statistician that we
are qualified neither by training nor experience to be.") (quot-
ing Ethyl Corp. v. EPA, 541 F.2d 1, 36 (D.C. Cir. 1976));
Chevron, U.S.A., Inc. v. Natural Res. Def. Council, Inc., 467
U.S. 837, 865-66 (1984) (acknowledging the EPA’s "great
expertise" in air quality matters).

   The required notice and comment periods detailed above,
see, e.g., 42 U.S.C. §§ 7409(a)(1)(B), (b)(1) & (2),
7426(a)(1), are further designed to allow EPA and state regu-
lators to receive broad inputs into the regulatory scheme.
Agency rulemaking is a "quasi-legislative power, . . . intended
to add substance to the Acts of Congress, to complete absent
but necessary details, and to resolve unexpected problems." 3
Jacob A. Stein et al., Administrative Law § 14.01. As a result,
inputs into the rulemaking process would ideally reflect not
               STATE OF NORTH CAROLINA v. TVA                 23
only scientific knowledge, but also the varied practical per-
spectives of industry and environmental groups. As David
Shapiro has explained, the rulemaking process has the bene-
fits of providing proactive instead of reactive control, creating
opportunities for notice and comment, allowing flexibility in
developing rules, and lowering the likelihood of disturbing
reliance interests. David L. Shapiro, The Choice of Rulemak-
ing or Adjudication in the Development of Administrative Pol-
icy, 78 Harv. L. Rev. 921, 930-37 (1965). Rulemaking can in
this manner take advantage of the attributes of legislative
hearings, albeit in a more focused and circumscribed manner.
Shapiro also observed that the general nature of rulemaking
enables uniform application across industries, lessens the like-
lihood of distortions caused by the influence of individualized
facts in cases, and also makes the resulting rules readily
accessible in a single location. Id. at 935-41.

   Injunctive decrees, of course, are rulemakings of a sort.
While expressing the utmost respect for the obvious efforts
the district court expended in this case, we doubt seriously
that Congress thought that a judge holding a twelve-day
bench trial could evaluate more than a mere fraction of the
information that regulatory bodies can consider. "Courts are
expert at statutory construction, while agencies are expert at
statutory implementation." Negusie v. Holder, 555 U.S. ___,
129 S. Ct. 1159, 1171 (2009) (Stevens, J., concurring in part
and dissenting in part). In fact, the district court properly
acknowledged that "public nuisance principles . . . are less
well-adapted than administrative relief to the task of imple-
menting the sweeping reforms that North Carolina desires."
North Carolina v. Tenn. Valley Auth., 593 F. Supp. 2d at 817.
As the District of Columbia Circuit has emphasized, courts
"would be less than candid if [they] failed to acknowledge
that [they] approach the task of examining some of the com-
plex scientific issues presented in cases of this sort with some
diffidence." Lead Indus. Ass’n, 647 F.2d at 1146.

   It is crucial therefore that courts in this highly technical
arena respect the strengths of the agency processes on which
24             STATE OF NORTH CAROLINA v. TVA
Congress has placed its imprimatur. Regulations and permits,
while hardly perfect, provide an opportunity for predictable
standards that are scientifically grounded and thus give rise to
broad reliance interests. TVA, for example, spent billions of
dollars on power generation units that supply electricity to
seven different states in the belief that its permits allowed it
to do so. There is no way to predict the effect on TVA or utili-
ties generally of supplanting operating permits with mandates
derived from public nuisance law, but one suspects the costs
and dislocations would be heavy indeed. Without a single sys-
tem of permitting, "[i]t would be virtually impossible to pre-
dict the standard" for lawful emissions, and "[a]ny permit
issued . . . would be rendered meaningless." Ouellette, 479
U.S. at 497 (quoting Illinois v. City of Milwaukee, 731 F.2d
at 414). This is because "for an uncertain length of time after
the agency issues the permit, the permit-holder would face the
very real threat that the inquiry into the validity of its permit
might be reopened in an altogether different forum."
Palumbo, 989 F.2d at 162. A company, no matter how well-
meaning, would be simply unable to determine its obligations
ex ante under such a system, for any judge in any nuisance
suit could modify them dramatically. Rather than take this
risk in the future, "otherwise worthy permit applicants will
weigh the formidable costs in delay and litigation, and simply
will not apply." Id.

   There are, therefore, a host of reasons why Congress pre-
ferred that emissions standards be set through agencies in the
first instance rather than through courts. The prospects of
forum shopping and races to the courthouse, the chances of
reversals on appeal, the need to revisit and modify equitable
decrees in light of changing technologies or subsequent enact-
ments, would most assuredly keep matters unsettled. Con-
gress opted instead for an expert regulatory body, guided by
and subject to congressional oversight, to implement, main-
tain, and modify emissions standards and to do so with the aid
of the rulemaking process and a cooperative partnership with
states. In the words of Ouellette addressing the similarly com-
               STATE OF NORTH CAROLINA v. TVA                25
prehensive Clean Water Act, the statute "carefully defines the
role of both the source and affected States, and specifically
provides for a process whereby their interests will be consid-
ered and balanced by the source State and the EPA." 479 U.S.
at 497. It is not open to this court to ignore the words of the
Supreme Court, overturn the judgment of Congress, supplant
the conclusions of agencies, and upset the reliance interests of
source states and permit holders in favor of the nebulous rules
of public nuisance.

                              IV.

   In addition to the problems noted above, the district court’s
decision compromised principles of federalism by applying
North Carolina law extraterritorially to TVA plants located in
Alabama and Tennessee. There is no question that the law of
the states where emissions sources are located, in this case
Alabama and Tennessee, applies in an interstate nuisance dis-
pute. The Supreme Court’s decision in Ouellette is explicit: a
"court must apply the law of the State in which the point
source is located." 479 U.S. at 487. While Ouellette involved
a nuisance suit against a source regulated under the Clean
Water Act, all parties agree its holding is equally applicable
to the Clean Air Act.

   Unfortunately, while the district court acknowledged the
proper standard, North Carolina v. Tenn. Valley Auth., 593 F.
Supp. 2d at 829 (citing Ouellette, 479 U.S. at 487), it for all
practical purposes applied North Carolina’s Clean Smoke-
stacks Act extraterritorially in Alabama and Tennessee. The
decision below does little more than mention the black letter
nuisance law of Alabama and Tennessee on its way to crafting
a remedy derived entirely from the North Carolina Act. See
id. at 829-31.

   Certainly North Carolina intended for its Clean Smoke-
stacks Act to be applied to TVA. We need look no further
than the direct statements of the North Carolina law itself.
26             STATE OF NORTH CAROLINA v. TVA
The Act orders the state to "use all available resources and
means, including . . . litigation to induce other states and enti-
ties, including the Tennessee Valley Authority, to achieve
reductions in emissions of oxides of nitrogen (NOx) and sulfur
dioxide (SO2) comparable to those required by [the Clean
Smokestacks Act] . . . on a comparable schedule." 2002 N.C.
Sess. Laws 4 § 10.

   Further, North Carolina repeatedly affirmed its desire to
apply the standards found in the Clean Smokestacks Act to
TVA. When the North Carolina Attorney General filed the
present lawsuit in 2006, he issued a press release stating that
"North Carolina is seeking a Court order requiring TVA to
control its emissions to levels similar to those required for
coal-fired power plants in North Carolina by the North Caro-
lina Clean Smokestacks Act on a similar timetable." And in
responding to TVA’s first interrogatory, North Carolina indi-
cated that it was requesting the imposition of "emission rates
equivalent to North Carolina’s Clean Smokestack[s] Act."
Even in opening statements before the district court, North
Carolina asked the court to require TVA to install controls "in
a similar way the State of North Carolina is requiring [in-state
power companies] Duke and Progress Energy by statute to put
pollution controls in their facilities."

   Nor did North Carolina change its tune once the bench trial
began. Its primary expert witness, Dr. James Staudt, reiterated
often his "opinion [that TVA was a public nuisance was]
based upon looking at the Clean Smokestacks Act and the
emission rates that would be required for the Clean Smoke-
stacks Act." Dr. Staudt stated that his "benchmark" was
"emissions rates that were equivalent to what would be
required in the Clean Smokestacks Act in 2013" and used
"those equivalent emission rates [to develop] what would be
caps for TVA." Indeed, Dr. Staudt believed his suggested
2013 deadline for installation of emissions controls was "an
appropriate deadline" because "it is consistent with the Clean
Smokestacks Act final deadline."
               STATE OF NORTH CAROLINA v. TVA                  27
   Importantly, in Plaintiff’s Exhibits 95 and 97 Dr. Staudt
summarized his findings and recommended installation of
scrubbers and SCRs to meet specific emissions caps for each
of TVA’s coal-fired electricity generation units. Plaintiff’s
Exhibit 95 showed precisely how many tons of SO2 and NOx
TVA’s system of eleven power plants as a whole would be
permitted to emit under the North Carolina Clean Smoke-
stacks Act. Plaintiff’s Exhibit 97, revealingly titled "CSA-
Equivalent 2013 Emissions," then gave a unit-by-unit break-
down of the emissions each TVA plant would produce if the
scrubbers and SCRs were installed per Dr. Staudt’s recom-
mendation. At the end of Plaintiff’s Exhibit 97, the sum total
of the TVA units’ emissions under Dr. Staudt’s proposed
scheme was just below the Clean Smokestacks Act caps pres-
ented in Plaintiff’s Exhibit 95.

   In light of the fact that North Carolina informed the district
court in its opening statement that Dr. Staudt would provide
this information and again referred to his proposals during
closing argument, it is not at all surprising that the district
court utilized Exhibit 97’s CSA-Equivalent 2013 Emissions
calculations in fashioning its injunction. The court essentially
granted plaintiff its request. It created "a judicially-imposed
injunction requiring the installation and continual, year-round
use of appropriate pollution control technology." North Caro-
lina v. Tenn. Valley Auth., 593 F. Supp. 2d at 831. As recom-
mended by Dr. Staudt, the injunction demanded installation of
scrubbers and SCRs on each electric generating unit at the
four plants closest to the North Carolina border and the con-
tinuous operation of those pollution controls once installed.
Id. at 832. It also adopted Dr. Staudt’s 2013 timeline for final
completion of all scrubber and SCR construction. Id. at 827,
832.

   Further, the court’s injunction traced, line by line, the emis-
sions caps that Dr. Staudt presented in Plaintiff’s Exhibit 97.
After ordering that "TVA shall adhere to the following caps
on emissions," id. at 832, the district court reproduced the
28             STATE OF NORTH CAROLINA v. TVA
portions of the CSA-Equivalent 2013 Emissions chart that
related to each of the twenty-two electric generating units at
the four plants it enjoined. Compare id. at 832-33 with J.A.
1111-12 (Plaintiff’s Ex. 97). For instance, the district court
capped emissions from electric generating unit number eight
at TVA’s Widows Creek plant in northeast Alabama at 860
tons of NOx and 4,508 tons of SO2 per year—the precise
amounts that Dr. Staudt proposed. Compare North Carolina
v. Tenn. Valley Auth., 593 F. Supp. 2d at 833 with J.A. 1112
(Plaintiff’s Ex. 97). Indeed, the court imposed the limitations
that Dr. Staudt calculated to show how TVA could meet the
demands of North Carolina’s Clean Smokestacks Act on
every single electric generating unit it enjoined.

   Yet the state now attempts to argue that the district court
did not, after all, impose the Clean Smokestacks Act extrater-
ritorially because it only imposed caps on the four of TVA’s
eleven plants that were closest to the North Carolina line.
North Carolina claims that because the Clean Smokestacks
Act demands only system-wide caps, Dr. Staudt’s plant-
specific calculations do not represent an extraterritorial appli-
cation of the law.

   But, as already explained, the district court’s emissions lim-
its on TVA’s four plants are clearly drawn from Dr. Staudt’s
calculations, which he testified that he created to provide a
remedy that would be "equivalent to the requirements of the
North Carolina Clean Smokestacks Act." North Carolina in
fact admits that "Exhibit 97 was intended to demonstrate at
least one way that TVA would be capable of meeting North
Carolina’s proposed system-wide caps for NOx and SO2 emis-
sions with the installation of scrubbers and SCRs." The fact
that there may have been other ways that TVA could reach
the emissions levels demanded by the Clean Smokestacks Act
and the fact that the district court ultimately decided to award
North Carolina only part of its requested relief cannot obscure
what occurred: The district court took the very calculations
provided by North Carolina to show how TVA could comply
                 STATE OF NORTH CAROLINA v. TVA                        29
with an extraterritorial application of its law and used them to
fashion an injunction.

   The Supreme Court emphasized that only source state law,
here that of Alabama and Tennessee, could impose more
stringent emission rates than those required by federal law on
plants located in those two jurisdictions. Ouellette, 479 U.S.
at 494-97. Yet exactly the opposite has happened. North Car-
olina explicitly stated that it wanted out-of-state entities,
including TVA, to follow its state rules. North Carolina law
provided the basis for Dr. Staudt’s opinion that TVA was
operating unreasonably. North Carolina law provided Dr.
Staudt with the benchmark for his recommendations regard-
ing the steps TVA should take to bring its plants into compli-
ance with the North Carolina Clean Smokestacks Act. And
North Carolina law ultimately provided the remedy the dis-
trict court adopted against the four TVA plants at issue here.
Its decision was tied so tightly to the North Carolina Clean
Smokestacks Act that it violates Ouellette’s directive that
source state law applies to interstate nuisance suits.

                                   V.

   Even were we to accept North Carolina’s claim that the dis-
trict court actually applied source state law from Alabama and
Tennessee, it would be difficult to uphold the injunctions
because TVA’s electricity-generating operations are expressly
permitted by the states in which they are located.2 It would be
odd, to say the least, for specific state laws and regulations to
expressly permit a power plant to operate and then have a
generic statute countermand those permissions on public nui-
  2
    The parties also dispute whether Alabama and Tennessee allow out-of-
state sovereigns to bring public nuisance suits on behalf of their out-of-
state citizens. TVA as well as Alabama as intervenor argue with some
force that the district court’s decision that North Carolina could enforce
source state public nuisance law as a "foreign quasi sovereign" has no
basis in Alabama and Tennessee law. Our resolution of the other issues in
this case makes it unnecessary for us to resolve this issue.
30             STATE OF NORTH CAROLINA v. TVA
sance grounds. As the Supreme Court has made clear,
"[s]tates can be expected to take into account their own nui-
sance laws in setting permit requirements." Ouellette, 479
U.S. at 499.

   While North Carolina points out that an activity need not
be illegal in order to be a nuisance, that is not the situation
before us. There is a distinction between an activity that is
merely not illegal versus one that is explicitly granted a per-
mit to operate in a particular fashion. "Courts 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). This is especially true "where the
conduct sought to be enjoined implicates the technically com-
plex area of environmental law." Id.; see also Restatement
(Second) of Torts § 821B cmt. f. ("Although it would be a
nuisance at common law, conduct that is fully authorized by
statute, ordinance or administrative regulation does not sub-
ject the actor to tort liability.").

   Alabama law certainly recognizes this principle. The Ala-
bama Supreme Court has repeatedly explained that "there can
be no abatable nuisance for doing in a proper manner what is
authorized by law." Fricke v. City of Guntersville, 36 So. 2d
321, 322 (Ala. 1948) (quoting Branyon v. Kirk, 191 So. 345,
349 (Ala. 1939)) (emphasis added); see also City of Birming-
ham v. City of Fairfield, 375 So. 2d 438, 441 (Ala. 1979)
(same); Johnson v. Bryant, 350 So. 2d 433, 436 (Ala. 1977)
(same); City of Birmingham v. Scogin, 115 So. 2d 505, 512
(Ala. 1959) (same). The law draws a distinction between
activities which are merely not illegal, see Ala. Code § 6-5-
120, and those which are expressly permitted. Thus, an entity
must behave in a negligent manner if its expressly permitted
activities are to constitute a nuisance. See City of Birmingham
v. City of Fairfield, 375 So. 2d at 441-43; St. Louis-San Fran-
cisco Ry. Co. v. Wade, 607 F.2d 126, 131 n.6 (5th Cir. 1979)
(Under Alabama law, "[n]egligence is an element of a claim
                STATE OF NORTH CAROLINA v. TVA                  31
for nuisance . . . if the defendant’s activities are specifically
authorized by law.").

   So too Tennessee. An activity that is explicitly licensed and
allowed by Tennessee law cannot be a public nuisance. See,
e.g., O’Neil v. State ex rel. Baker, 206 S.W.2d 780, 781
(Tenn. 1947); Fey v. Nashville Gas & Heating Co., 64 S.W.2d
61, 62 (Tenn. Ct. App. 1933). Additionally, Tennessee’s Dep-
uty Air Director, one of the officials responsible for managing
the air permitting process, testified that in issuing emissions
permits the state takes into account the same factors that
would be considered by a court in a nuisance case. The only
way that a permit-authorized activity can be enjoined under a
nuisance theory is if it is operating negligently, a claim not
before us in this case. See Fey, 64 S.W.2d at 62. Thus while
it is technically accurate to state that an act that is not illegal
can still be a nuisance, that proposition is simply not relevant
in this case because TVA’s Tennessee plants are expressly
permitted to operate as they do. As TVA’s facilities operate
under permits, required by Congress and EPA regulations, we
cannot say that the plant emissions of which North Carolina
complains are a public nuisance.

   In sum, TVA’s plants cannot logically be public nuisances
under Alabama and Tennessee law where TVA is in compli-
ance with EPA NAAQS, the corresponding state SIPs, and the
permits that implement them. These standards impose more
stringent requirements than source state nuisance law. Ala-
bama and Tennessee nuisance law only prohibits activities
that substantially interfere with the average person—for
example, a person of "ordinary health and sensibilities, and
ordinary modes of living," Jenkins v. CSX Transp., Inc., 906
S.W.2d 460, 462 (Tenn. Ct. App. 1995) (emphasis added), or
"an ordinary reasonable man," Ala. Code § 6-5-120 (empha-
sis added); see also Fowler v. Fayco, Inc., 275 So. 2d 665,
669 (Ala. 1973) (nuisance not intended to prevent harms that
would "affect only one of a fastidious taste") (quoting Ala.
Code § 6-5-120).
32             STATE OF NORTH CAROLINA v. TVA
   In contrast, the EPA’s regulations regarding NAAQS and
the SIPs implementing them are understandably designed to
protect even those individuals particularly sensitive to emis-
sions. "NAAQS must protect not only average healthy indi-
viduals, but also ‘sensitive citizens’—children, for example,
or people with asthma, emphysema, or other conditions ren-
dering them particularly vulnerable to air pollution." Am.
Lung Ass’n v. EPA, 134 F.3d 388, 389 (D.C. Cir. 1998). This
case does not join the issue of whether TVA is in compliance
with the various permits under which it operates, and we
assume, without deciding, that it is. If TVA is in compliance
with the more demanding federal EPA requirements and state
law SIPs, it cannot be in violation of less-stringent state law
nuisance standards.

                              VI.

   While we must overturn the district court’s injunction,
North Carolina is by no means without remedy. As already
noted, the section 126 process provides protection for states
that believe they are suffering from improper interstate pollu-
tion. "[D]ownwind states retain their statutory right to petition
for immediate relief from unlawful interstate pollution under
section 126, 42 U.S.C. § 7426." North Carolina v. EPA, 531
F.3d 896, 930 (D.C. Cir. 2008) (per curiam). This section is
the primary process for states to address interstate emissions
that they believe cause problems with their attainment of
NAAQS.

   Indeed, North Carolina has already filed section 126 claims
with regard to the very TVA plants against which it sought
public nuisance rulings in this case. The district court recog-
nized that "even in the present dispute, North Carolina began
its pursuit of relief by utilizing the normal administrative
channels established by the CAA." North Carolina v. Tenn.
Valley Auth., 593 F. Supp. 2d at 816. The EPA initially denied
North Carolina’s petition because it believed a new set of reg-
ulations it had promulgated, known as the Clean Air Interstate
               STATE OF NORTH CAROLINA v. TVA                 33
Rule (CAIR), 70 Fed. Reg. 25,162 (May 12, 2005), would
address the state’s concerns. However, after the D.C. Circuit
reversed CAIR because it believed aspects of the rule were
inconsistent with the Clean Air Act, see North Carolina v.
EPA, 531 F.3d at 901, it also remanded North Carolina’s sec-
tion 126 claims for further EPA consideration in light of its
decision. See Sierra Club v. EPA, 313 Fed. Appx. 331 (D.C.
Cir. 2009) (per curiam). Those claims remain pending, and
there is no suggestion that the process will fail to provide
North Carolina with a full and fair venue for airing its con-
cerns.

   Nor is section 126 the only remedy North Carolina could
invoke. By federal law, states are required to provide com-
ment periods before SIPs can be issued or modified, and
North Carolina "had the opportunity to protect [its] interests
before the fact by commenting and objecting to the proposed
standard." Ouellette, 479 U.S. at 498 n.18. It apparently chose
not to do so, and cannot complain now that it desires a differ-
ent resolution. However, if either Tennessee or Alabama
decides to modify its SIP in the future, North Carolina will
have ample opportunity to make its views known. In addition,
SIPs must provide for written notice before a new source can
be constructed or an existing source can be modified. 42
U.S.C. § 7426(a)(1). This notice must be given to any region
that may be affected before such changes can take place. Id.
And should any of these avenues fail to satisfy the state, the
Clean Air Act allows petitions for judicial review of a broad
range of EPA actions, including promulgation of air standards
and EPA approval of SIPs, see 42 U.S.C. § 7607(b)(1), while
Alabama and Tennessee laws provide for similar administra-
tive and judicial appeals of state permitting decisions, see Ala.
Code §§ 22-22A-6(a)(4), 22A-7(c)(6); Tenn. Code §§ 68-201-
105(a)(1), 68-201-108(a), 4-5-322.

   This list of possible remedies does not even include private
law remedies that may be available to North Carolina. Indeed,
if North Carolina believes that TVA is not complying with its
34             STATE OF NORTH CAROLINA v. TVA
permits, the Clean Air Act provides for suits "against any per-
son . . . who is alleged to have violated . . . or to be in viola-
tion of (A) an emission standard or limitation under this
chapter or (B) an order issued by the Administrator or a State
with respect to such a standard or limitation." 42 U.S.C.
§ 7604(a)(1). The statute further grants a cause of action
against the EPA if it fails to perform any non-discretionary
responsibility, 42 U.S.C. § 7604(a)(2), and also allows suit
against any entity that constructs a source of emissions with-
out securing the requisite permits. 42 U.S.C. § 7604(a)(3). If
North Carolina believes that any of these violations have
occurred, it remains free to pursue such avenues as well.

   As this non-exclusive discussion of remedies demonstrates,
North Carolina has a number of possible paths to pursue in its
entirely laudable quest to guarantee pure air to its citizens.
Seeking public nuisance injunctions against TVA, however, is
not an appropriate course. The laws in place have been
designed by Congress to protect our air and water. Plaintiff
would replace them with an unknown and uncertain litigative
future. As the Supreme Court has emphasized, the legal diffi-
culties with this approach are legion. No matter how lofty the
goal, we are unwilling to sanction the least predictable and the
most problematic method for resolving interstate emissions
disputes, a method which would chaotically upend an entire
body of clean air law and could all too easily redound to the
detriment of the environment itself.

                              VII.

   For the foregoing reasons, we reverse the judgment of the
district court and remand with directions to dismiss the action.

                               REVERSED AND REMANDED
