In the

United States Court of

Appeals

For the Seventh Circuit

No. 10-3891

STATE OF MICHIGAN, et al.,

Plaintiffs-Appellants,

and

GRAND TRAVERSE BAND OF OTTAWA

AND CHIPPEWA INDIANS,

Intervenor-Appellant,

v.

UNITED STATES ARMY CORPS OF

ENGINEERS, et al.,

Defendants-Appellees,

and

CITY OF CHICAGO, et al.,

Intervenors-Appellees.

Appeal from the United States District Court

for the Northern District of Illinois, Eastern Division.

No. 10 C 4457—Robert M. Dow, Jr., Judge.
2 No. 10-3891

ARGUED MAY 5, 2011 — DECIDED AUGUST 24, 2011

*

Before MANION, WOOD, and WILLIAMS, Circuit Judges.

WOOD, Circuit Judge. Ambitious engineering projects that

began at the time that the City of Chicago was founded have

established a waterway in northeastern Illinois that connects

Lake Michigan to the Mississippi watershed. (Additional

links between the Mississippi and the Great Lakes exist

elsewhere, from northern Minnesota to New York.) The

system of canals, channels, locks, and dams, with which we

are concerned, known today as the Chicago Area Waterway

System (or CAWS, as the parties call it in their briefs), winds

from the mouth of the Chicago River and four other points

on Lake Michigan to tributaries of the Mississippi River in

Illinois. The navigable link has been a boon to industry and

commerce, and it supports transportation and recreation.

Public health crises that once were common because the

Chicago River emptied the City’s sewage into the lake – the

City’s freshwater supply – vanished thanks to the Chicago

Sanitary and Ship Canal, which reversed the flow of the

Chicago River so that it now pulls water from the lake, into

the CAWS, and down toward the Mississippi. During heavy

rains and seasonal high waters in the region, the CAWS is

used to control flooding.

This effort to connect the Great Lakes and Mississippi

watersheds has not been without controversy. At the turn of

the 20th century, Missouri sued in the Supreme Court to

stop Illinois from opening the Sanitary and Ship Canal. An

opinion by Justice Holmes rejected Missouri’s challenge; the

Court concluded that the state had not presented enough

evidence to establish that the flow of sewage toward the

 This opinion is released in typescript; a printed

*

version will follow.
No. 10-3891 3

Mississippi would create a public nuisance. Missouri v.

Illinois, 200 U.S. 496 (1906); see also Missouri v. Illinois, 180

U.S. 208 (1901). Several years later a broader fight erupted

among the states bordering the Great Lakes, and the Court

began to issue decrees setting the maximum rate at which

Illinois may divert water away from Lake Michigan and into

the CAWS. E.g., Wisconsin v. Illinois, 449 U.S. 48 (1980);

Wisconsin v. Illinois, 388 U.S. 426 (1967); Wisconsin v. Illinois,

311 U.S. 107 (1940); Wisconsin v. Illinois, 278 U.S. 367 (1929).

Nor has opening a pathway between these bodies of fresh

water come without costs. This appeal requires us to

consider one of those costs: the environmental and economic

harm posed by two invasive species of carp, commonly

known as Asian carp, which have migrated up the

Mississippi River and now are poised at the brink of this

man-made path to the Great Lakes. The carp are voracious

eaters that consume small organisms on which the entire

food chain relies; they crowd out native species as they enter

new environments; they reproduce at a high rate; they travel

quickly and adapt readily; and they have a dangerous habit

of jumping out of the water and harming people and

property.

In an attempt to stop the fish, Michigan, Minnesota, Ohio,

Pennsylvania, and Wisconsin, all states bordering the Great

Lakes, filed this lawsuit against the U.S. Army Corps of

Engineers (the Corps) and the Metropolitan Water

Reclamation District of Greater Chicago (the District), which

together own and operate the facilities that make up the

CAWS. The plaintiff states allege that the Corps and the

District are managing the CAWS in a mannerthat will allow

invasive carp to move for the first time into the Great Lakes.

The states fear that if the fish establish a sustainable

population there, ecological disaster and the collapse of

billion-dollar industries that depend on the existing

ecosystem will follow. They say that the defendants’ failure

to close down parts of the CAWS to avert the crisis creates

a grave risk of harm, in violation of the federal common law

of public nuisance, see American Electric Power Co., Inc. v.
4 No. 10-3891

Connecticut, 131 S. Ct. 2527 (2011), and they advance a

related claim against the Corps based on the Administrative

Procedure Act (APA), 5 U.S.C. § 702. The states asked the

district courtfor declaratory and injunctive relief and moved

for a preliminary injunction that would require the

defendants to put in place additional physical barriers

throughout the CAWS, implement new procedures to stop

invasive carp, and expedite a study of how best to separate

the Mississippi and Great Lakes watersheds permanently.

Other parties intervened to protect their interests – the

Grand Traverse Band of Ottawa and Chippewa Indians on

the side of the plaintiffs, and the City of Chicago, Wendella

Sightseeing Company, and the Coalition to Save Our

Waterways as defendants. The district court denied the

motion for a preliminary injunction, and the states appealed

immediately. See 28 U.S.C. § 1292(a)(1).

We conclude that the court’s decision to deny preliminary

relief was not an abuse of discretion. Our analysis, however,

differs in significant respects from that of the district court,

which was persuaded that the plaintiffs had shown only a

minimal chance of succeeding on their claims. We are less

sanguine about the prospects of keeping the carp at bay. In

our view, the plaintiffs presented enough evidence at this

preliminary stage of the case to establish a good or perhaps

even a substantial likelihood of harm – that is, a non-trivial

chance that the carp will invade Lake Michigan in numbers

great enough to constitute a public nuisance. If the invasion

comes to pass, there is little doubt that the harm to the

plaintiff states would be irreparable. That does not mean,

however, that they are automatically entitled to injunctive

relief. The defendants, in collaboration with a great number

of agencies and experts from the state and federal

governments, have mounted a full-scale effort to stop the

carp from reaching the Great Lakes, and this group has

promised that additional steps will be taken in the near

future. This effort diminishes any role that equitable relief

would otherwise play. Although this case does not involve

the same kind of formal legal regime that caused the
No. 10-3891 5

Supreme Court to find displacement of the courts’ commonlaw powers in American Electric Power, on the present state

of the record we have something close to it. In light of the

active regulatory efforts that are ongoing, we conclude that

an interim injunction would only get in the way. We stress,

however, that if the agencies slip into somnolence or if the

record reveals new information at the permanent injunction

stage, this conclusion can be revisited.

I

To justify a preliminary injunction, the plaintiff states

must show that they are likely to succeed on the merits of

their claims, that they are likely to suffer irreparable harm

without an injunction, that the harm they would suffer

without the injunction is greater than the harm that

preliminary relief would inflict on the defendants, and that

the injunction is in the public interest. Winter v. Natural Res.

Def. Council, Inc., 555 U.S. 7, 20 (2008). We will affirm the

decision to deny a preliminary injunction unless the district

court has abused its discretion. Judge v. Quinn, 612 F.3d 537,

557 (7th Cir. 2010). As usual, we review questions of fact for

clear error and questions of law de novo. Girl Scouts of

Manitou Council, Inc. v. Girl Scouts of United States of Am., Inc.,

549 F.3d 1079, 1086-87 (7th Cir. 2008).

II

We begin with the states’ likelihood of succeeding on their

common law public nuisance claim. The district court

thought that the states had “at best, a very modest likelihood

of success.” For the reasons discussed below, we think that

the district court underestimated the likely merit of the

states’ claim, particularly at this early stage of the case.

A

The Supreme Court recently reminded us that when it

said, “There is no federal general common law,” in Erie
6 No. 10-3891

Railroad Co. v. Tompkins, 304 U.S. 64, 78 (1938), it did not

close the door on federal common law entirely. American

Electric Power, 131 S. Ct. at 2535-37. Instead, following Erie,

a “keener understanding” of federal common law

developed, under which federal courts “fill in ‘statutory

interstices,’ and, if necessary, even ‘fashion federal law’” in

areas “‘within national legislative power.’” Id. at 2535

(quoting Henry J. Friendly, In Praise of Erie - And of the New

Federal Common Law, 39 N.Y.U. L. Rev. 383 (1964)). In

American Electric Power, the Court reaffirmed a long line of

cases that have “approved federal common law suits

brought by one State to abate pollution emanating from

another State.” 131 S. Ct. at 2535-36. These decisions reach at

least as far back as the battle between Missouri and Illinois

over sewage, see Missouri v. Illinois, supra, and they have

continued from there, see Georgia v. Tennessee Copper Co., 206

U.S. 230 (1907), New York v. New Jersey, 256 U.S. 296 (1921),

New Jersey v. City of New York, 283 U.S. 473 (1931), Illinois v.

City of Milwaukee, 406 U.S. 91 (1972) (Milwaukee I), City of

Milwaukee v. Illinois, 451 U.S. 304 (1981) (Milwaukee II), and

American Electric Power, 131 S. Ct. 2527. But it has been

recognized for a much longer period that the equitable

power of the courts extends to suits to abate public

nuisances. See United Steelworkers of America v. United States,

361 U.S. 39, 60-61 (1959) (Frankfurter, J., concurring)

(assembling examples from 16th century England to the turn

of the 20th century in the United States).

It is our federal system that creates the need for a federal

common law to govern interstate disputes over nuisances.

Tennessee Copper explains that when the states joined the

union and in so doing abandoned theirright to abate foreign

nuisances by force, “they did not thereby agree to submit to

whatever might be done. They did not renounce the

possibility of making reasonable demands on the ground of

their still remaining quasi-sovereign interests; and the

alternative to force is a suit in this court.” 206 U.S. at 237. A

state that wants to bring a lawsuit attacking a nuisance

emanating from outside of its borders faces at least two legal
No. 10-3891 7

difficulties: whom to sue, and what law to apply? If the

offender is another state, then the Constitution permits an

original action in the Supreme Court.U.S.CONST. Art. III sec.

2, cl. 5. Whatever the venue, applicable law is a problem: the

offending state owes no allegiance to the law of the plaintiff

state, but the plaintiff state may rightly fear protectionism if

the law of the offending state is used. Committee for

Consideration of Jones Falls Sewage Sys. v. Train, 539 F.2d 1006,

1008 (4th Cir. 1976) (en banc). Responding to this concern, the

Court has concluded that in the context of interstate

nuisances “where there is an overriding federal interest in

the need for a uniform rule of decision or where the

controversy touches basic interests of federalism,” federal

common law governs. Milwaukee I, 406 U.S. at 105 n.6. When

evaluating claims based on the federal common law of

nuisance, courts must be mindful that they do not have

“creative power akin to that vested in Congress.” American

Electric Power, 131 S. Ct. at 2536.

1

The states’ public nuisance action here is based on

allegations that non-native species of carp (specifically,

bighead and silver carp) will migrate through waterworks

operated by the defendants from rivers connected to the

Mississippi into Lake Michigan and on to the other Great

Lakes. “When we deal with air and water in their ambient

and interstate aspects, there is a federal common law.”

Milwaukee I, 406 U.S. at 103. We know that this body of law

applies in a dispute about “the pollution of a body of water

such as Lake Michigan bounded, as it is, by four States,” id.

at 105 n.6. But the Court has cautioned that it has never

“held that a State may sue to abate any and all manner of

pollution originating outside its borders.” American Electric

Power, 131 S. Ct. at 2536. The Corps and the District contend

that the common law does not extend to the allegations in

this case. They stress that they are not emitting “traditional

pollutants”; all they have done, they say, is to operate

facilities in the CAWS through which invasive species

already living in local rivers might travel on their own. We
8 No. 10-3891

can dismiss the latter part of this argument without much

discussion: the defendants bear responsibility for nuisances

caused by their operation of a manmade waterway between

the Great Lakes and Mississippi watersheds. That they are

not themselves physically moving fish from one body of

waterto the other does not mean that their normal operation

of the CAWS cannot cause a nuisance. See, e.g.,

RESTATEMENT (SECOND) TORTS § 834 (“One is subject to

liability for a nuisance caused by an activity, not only when

he carries on the activity but also when he participates to a

substantial extent in carrying it on.”) & cmt. (b) (defining

“activity” to include acts “that create physical conditions

that are harmful to neighboring land after the activity that

created them has ceased”).

Similarly, we know of no rule saying that the defendants

must emit a “traditional pollutant” in order for federal

common law to apply. While it may be true that the

introduction of an invasive species of fish into a new

ecosystem does not fit the concept of nuisance as neatly as

a spill of toxic chemicals into a stream, we do not think the

Supreme Court has limited the concept of public nuisance as

much as the defendants suggest. A public nuisance is

defined as a substantial and unreasonable interference with

a right common to the general public, usually affecting the

public health, safety, peace, comfort, or convenience.

RESTATEMENT (SECOND) TORTS § 821B; DAN B. DOBBS, THE

LAW OF TORTS § 467, at 1334 (2000). It would be arbitrary to

conclude that this type of action extends to the harm caused

by industrial pollution but not to the environmental and

economic destruction caused by the introduction of an

invasive, non-native organism into a new ecosystem

(assuming that the states have correctly forecast the

depletion of the Great Lakes fishery and the corresponding

damage to the multi-billion-dollar sports fishing industry).

Public nuisance traditionally has been understood to cover

a tremendous range of subjects:

It includes interferences with the public health, as in the

case of a hogpen, the keeping of diseased animals, or a
No. 10-3891 9

malarial pond; with the public safety, as in the case of

the storage of explosives, the shooting of fireworks in

the streets, harboring a vicious dog, or the practice of

medicine by one not qualified; with public morals, as in

the case of houses of prostitution, illegal liquor

establishments, gambling houses, indecent exhibitions,

bullfights, unlicensed prize fights, or public profanity;

with the public peace, as by loud and disturbing noises,

or an opera performance which threatens to cause a riot;

with the public comfort, as in the case of bad odors,

smoke, dust and vibration; with public convenience, as

by obstructing a highway or a navigable stream, or

creating a condition which makes travel unsafe or

highly disagreeable, or the collection of an inconvenient

crowd; and in addition, such unclassified offenses as

eavesdropping on a jury, or being a common scold.

KEETON, et al., PROSSER AND KEETON ON TORTS § 90, at 643-45

(5th ed. 1984) (citations omitted). The Supreme Court’s

application of public nuisance principles to cases involving

shared water resources reflects this broad understanding.

For example, the Court has held that a change in one state’s

water-drainage system that causes flooding on another

state’s farms may create a public nuisance, see North Dakota

v. Minnesota, 263 U.S. 365, 374 (1923); just as the industrial

contamination of a body of water might, Arizona Copper Co.

v. Gillespie, 230 U.S. 46, 57 (1913). In this vein, American

Electric Power emphasized “that public nuisance law, like

common law generally, adapts to changing scientific and

factual circumstances.” 131 S. Ct. at 2536. The types of

invasive carp that are the concern in this case have been

designated as injurious species by the U.S. Fish and Wildlife

Service, see 50 C.F.R. § 16.13(a)(2)(v); this designation means

that it is a federal crime under the Lacy Act to transport

them around or into the United States, 16 U.S.C. §§ 3371-78.

We conclude that the federal common law of public

nuisance extends to the problem that the plaintiff states have

identified.

2
10 No. 10-3891

The next question, which is raised only by the Corps, is

whether the plaintiff states may state a claim based on the

federal common law of public nuisance against the United

States. The Corps asserts that “the States have shown no

basis forrecognizing a federal common-law public nuisance

claim against a federal agency.” But the Corps has not

developed the argument much beyond this broad statement.

Its brief moves instead to a discussion of whether federal

common law has been displaced by congressional legislation

and whether there is any role for the courts to play when

agencies have taken concerted action to address a problem.

These are two important issues that we will explore below,

but neither point explains why a claim based on the federal

common law of public nuisance cannot move forward

against the United States. The plaintiff states have done little

to counter the Corps’s suggestion. They reply

(unresponsively, in our view) that “the federal common law

of public nuisance undoubtedly exists.”

The implications of finding that the United States has

created a public nuisance strike us as potentially important

and complex; this is not a topic that can be thrown on the

table and then ignored. In this connection, it is telling that

the Supreme Court went out of its way in American Electric

Power to point out that it “ha[d] not yet decided whether

private citizens . . . or political subdivisions . . . of a State

may invoke the federal common law of nuisance to abate

out-of-state pollution.” 131 S. Ct. at 2536. It declined to

answerthat question because it thought it best to resolve the

case on other grounds. But the Court’s statement cautions us

to tread carefully whenever we consider how far to push a

theory of federal common law. This concern is less pressing

for claims the Court has already recognized, such as those

against state or local governmental entities or private

parties. See, e.g., Missouri v. Illinois, 200 U.S. 496 (states),

Milwaukee I, 406 U.S. 91 (political subdivisions); Tennessee

Copper, 206 U.S. 230 (private citizens).

We have not discovered any case in which the Supreme

Court has expressly authorized a public nuisance action
No. 10-3891 11

against the United States in its sovereign capacity. A recent

concurring opinion in the D.C. Circuit makes the same

observation, noting that “the Court has not endorsed any

federal common-law causes of action against the

Government during the post-Erie period.” El-Shifa Pharm.

Indus. Co. v. United States, 607 F.3d 836, 853 (D.C. Cir. 2010)

(Kavanaugh, J., concurring). To understand common-law

public nuisance in a way that would exclude suits against

the United States would be faithful to the ancient origins of

nuisance, where the term described the criminal act of

infringing on the rights of the Crown, see William L. Prosser,

Private Action for Public Nuisance, 52 Va. L. Rev. 997, 998

(1966); at least during that era, no one would have

contemplated that the King or Queen could be the source of

a nuisance. Whether this sort of sovereign prerogative has

any place in modern American law, as a concept distinct

from the sovereign immunity of the United States, is a

separate question. Perhaps there is also a modern

justification for the position that the federal common law of

public nuisance cannot operate against the government: this

area of federal common law exists to provide a uniform rule

for interstate disputes that will serve the national interest,

and it may be thought illogical to say that a federal actor,

which in theory embodies the national interest, is at the

same time violating a judge-made concept of that same

interest.

On the other hand, there are respectable arguments in

favor of applying public nuisance to the acts of federal

agencies, depending on the activity in which the agency is

engaged. We have moved far beyond the Divine Right of

Kings and the concept that the Crown can do no wrong. We

may assume that an agency’s effort to regulate private actors

in a particular area would not give rise to a claim of public

nuisance. But it is hard to see why the United States’s

ownership of a dam, power plant, or other facility should

automatically foreclose a public nuisance claim brought by

a state for harms created by the operation of that facility. If

the facility were located in and owned by State A and it was
12 No. 10-3891

damaging State B, then State B would be entitled to assert a

common-law claim against State A (or one of its

subdivisions or private citizens). Our case offers a good

illustration of the point: the Corps and the District together

operate facilities that are allegedly on the verge of creating

a nuisance in waters of the plaintiff states; why should the

plaintiffs be able to state a claim against the District but not

the Corps?

The possible inconsistencies that would be created by such

a rule may be the reason that no court has expressed concern

about the appearance of the Tennessee Valley Authority – a

federally owned entity that was created by Congress and

acts like a private corporation – as a defendant in a public

nuisance lawsuit. See American Electric Power, 131 S. Ct. 2527;

North Carolina ex rel. Cooper v. TVA, 615 F.3d 291 (4th Cir.

2010); North Carolina ex rel. Cooper v. TVA, 515 F.3d 344 (4th

Cir. 2008). In fact, out of all public nuisance decisions we

have identified from either the Supreme Court orthe Courts

of Appeals that involve a federal agency as a defendant,

none contains a whisper of discussion about whether the

claim runs against the United States. In addition to the cases

just mentioned, see MiddlesexCnty. Sewerage Auth. v. National

Sea Clammers Ass’n, 453 U.S. 1, 4 & n.3 (1981) (claims against

the Environmental Protection Agency and the Corps);

Committee for Consideration of Jones Falls Sewage Sys., 539 F.2d

1006 (claims against the EPA); Massachusetts v. U.S. Veterans

Admin., 541 F.2d 119 (1st Cir. 1976) (claims against the

Veterans Administration). Whether the plaintiffs’ commonlaw action can proceed against the Corps is a question that

may well require attention as this case proceeds. Given the

parties’ cursory exposition of the issue and our ultimate

conclusion that preliminary relief is not warranted, we find

it unnecessary to say more at this point. (We see this as a

question relating to the plaintiffs’ ability to state a claim; it

does not implicate the court’s jurisdiction, and so there is

nothing to prevent our declining to reach it.) For now, we

will assume that the states’ federal common-law claim may

proceed against all of the defendants.
No. 10-3891 13

B

The defendants argue that two additional obstacles also

diminish the states’ likelihood of succeeding on their public

nuisance claim. The first concerns the sovereign immunity

of the United States. The Corps contends that even if it

makes sense to apply public nuisance principles against the

United States, the Corps is nevertheless not subject to suit

because the United States has not waived its sovereign

immunity for this kind of claim. The second argument,

which we address below, is that congressional regulation of

the invasive carp problem has displaced any role for federal

common law.

“Absent a waiver, sovereign immunity shields the Federal

Government and its agencies from suit.” F.D.I.C. v. Meyer,

510 U.S. 471, 475 (1994). The Corps takes the position that

there is no such waiver of immunity for lawsuits against the

United States that seek declaratory and injunctive relief

based on a federal common-law tort. Whether this is correct

depends on the interaction between section 702 of the APA

and the Federal Tort Claims Act (FTCA), 28 U.S.C. § 1346(b).

We begin with a look at the APA. Section 702 reads as

follows:

A person suffering legal wrong because of agency

action, or adversely affected or aggrieved by agency

action within the meaning of a relevant statute, is

entitled to judicial review thereof. An action in a court

of the United States seeking relief other than money

damages and stating a claim that an agency or an officer

or employee thereof acted or failed to act in an official

capacity or under color of legal authority shall not be

dismissed nor relief therein be denied on the ground

that it is against the United States or that the United

States is an indispensable party.

5 U.S.C. § 702. “The first and second sentences of § 702 play

quite different roles.” Veterans for Common Sense v. Shinseki,

644 F.3d 845, 866 (9th Cir. 2011). The first supplies a right to
14 No. 10-3891

seek review of agency action; the second, added by the 1976

amendments to the statute, provides a waiver of sovereign

immunity. Id. The waiver covers actions that seek specific

relief other than money damages; this aptly describes the

plaintiffs’ claim for declaratory and injunctive relief. See

Blagojevich v. Gates, 519 F.3d 370, 371-72 (7th Cir. 2008)

(noting that § 702 “waived sovereign immunity for most

forms of prospective relief”); see also Bowen v. Massachusetts,

487 U.S. 879, 893 (1988) (construing § 702’s waiver broadly

and remarking that “complaints [for] declaratory and

injunctive relief . . . [are] certainly not actions for money

damages”); Veterans for Common Sense, 644 F.3d at 864-65.

Moreover, the waiver in § 702 is not limited to claims

brought pursuant to the review provisions contained in the

APA itself. The waiver applies when any federal statute

authorizes review of agency action, as well as in cases

involving constitutional challenges and other claims arising

underfederal law. Blagojevich, 519 F.3d at 372;Czerkies v. U.S.

Dep't of Labor, 73 F.3d 1435, 1437-38 (7th Cir. 1996) (en banc);

see also Veterans for Common Sense, 644 F.3d at 867-68;

Trudeau v. Federal Trade Comm’n, 456 F.3d 178, 186-87 (D.C.

Cir. 2006); United States v. City of Detroit, 329 F.3d 515, 520-21

(6th Cir. 2003) (en banc); Jaffee v. United States, 592 F.2d 712,

718 (3d Cir. 1979).

Although the United States has argued from time to time

that the “final agency action” requirement of § 704 limits the

waiver of immunity in § 702, it has not prevailed on that

ground. E.g., Veterans for Common Sense, 644 F.3d at 866-68;

Trudeau, 456 F.3d at 186-87. The Corps wisely does not take

that position here; as the Ninth Circuit explained recently,

the conditions of § 704 affect the right of action contained in

the first sentence of § 702, but they do not limit the waiver of

immunity in § 702+s second sentence. Veterans for Common

Sense, 644 F.3d at 866-68. The only limitation on § 702 that

requires our attention is the clause that says, “Nothing

herein . . . confers authority to grant relief if any other

statute that grants consent to suit expressly or impliedly

forbids the relief which is sought,” 5 U.S.C. § 702(2), which
No. 10-3891 15

Congress added to the statute at the same time that it

introduced the waiver of sovereign immunity, see Pub. L.

94-574, 90 Stat. 2721 (Oct. 21, 1976). Pointing to this

provision, the Corps frames an argument by negative

implication: it says that when Congress enacted the FTCA in

1946, it did so against a backdrop of no tort liability for the

United States; the FTCA waives the government’s sovereign

immunity in suits for money damages to the extent that a

private person would be held liable under applicable state

tort law, see 28 U.S.C. § 1346(b)(1); Smith v. United States, 507

U.S. 197, 201-02 (1993); Parrott v. United States, 536 F.3d 629,

635 (7th Cir. 2008); but while the FTCA authorizes actions

for damages, it says nothing at all about injunctive relief;

thus, the FTCA implicitly prohibits injunctive relief in tort

suits against the United States; and because of § 702(2), the

Corps’s argument concludes, the plaintiffs cannot use the

APA’s wavier of immunity to assert a common-law tort

claim against the United States.

That argument reads too much into congressional silence.

The FTCA authorizes various tort claims for damages

against the government to the extent that state law would

provide relief, and it spells out a number of explicit

exceptions. E.g., 28 U.S.C. § 2674 (barring punitive damages

and interest before judgment); id. § 2680 (limiting the waiver,

among other circumstances, where the alleged tort concerns

the government’s enforcement of a statute or a discretionary

function). There is nothing in the statute suggesting that

Congress meant to forbid all actions that were not expressly

authorized. To the contrary, section 702(2) requires evidence,

in the form of either express language or fair implication,

that Congress meant to forbid the relief that is sought. The

Corps’s effort to transform silence into implicit prohibition

would seriously undermine Congress’s effort in the APA to

authorize specific relief against the United States. When

Congress amended the APA in 1976 it gave every indication

that it intended to provide specific relief for all nonstatutory

claims against the government. See Trudeau, 456 F.3d at

186-87 (noting that all the reports from Congress “identified
16 No. 10-3891

as the measure’s clear purpose elimination of the sovereign

immunity defense in all equitable actions” and that “the

Senate Report plainly indicated that Congress expected the

waiverto apply to nonstatutory actions”) (internal quotation

marks and alterations removed); Jaffee, 592 F.2d at 718-19

(outlining the reasons for the amendments to § 702, the

concern that some executive departments were hiding

behind their immunity, and concluding, “It was therefore

precisely for equitable actions under section 1331 that

Congress enacted the amendments to section 702“).

The D.C. Circuit has read the Tucker Act, which it

interprets as the exclusive remedy for contract claims

against the government, to include an implicit prohibition

against specific relief in contract actions against the United

States and thus to prevent reliance on the APA’s waiver of

immunity in such cases. Sharp v. Weinberger, 798 F.2d 1521,

1523-24 (D.C. Cir. 1986) (Scalia, J.). But the same court has

since decided that, whatever the unspoken effect of the

Tucker Act may be, the FTCA does not contain a comparable

implicit ban against specific relief in tort cases against the

government, and thus that plaintiffs in such cases may take

advantage of the waiver in § 702 of the APA. U.S. Info.

Agency v. Krc, 989 F.2d 1211, 1216 (D.C. Cir. 1993). To the

same effect, we recently explained that while “[t]he tort

claims act doesn’t authorize equitable relief . . . . the

Administrative Procedure Act does,” and we went on to say

that a plaintiff asserting a tort claim against a federal agency

could take advantage of the APA to obtain equitable relief.

Robinson v. Sherrod, 631 F.3d 839, 841 (7th Cir. 2011).

If that were not reason enough to reject the Corps’s

immunity defense, there is more. By its terms, the FTCA

does not apply to any federal common-law tort claim, no

matter what relief is sought. As the Corps itself points out,

state tort law – not federal law – is the source of substantive

liability under the FTCA. See Meyer, 510 U.S. at 478-79;

Sobitan v. Glud, 589 F.3d 379, 388-89 (7th Cir. 2009); cf. Smith,

507 U.S. at 198 (no FTCA claim for tort committed in

Antarctica, a sovereignless entity not subject to either state
No. 10-3891 17

law or the law of a foreign country). The states’ tort claim is

based entirely on federal common law, and so the claim

would not be cognizable under the FTCA in the first place.

Meyer, 510 U.S. at 478. And if the FTCA could never apply to

the type of claim advanced, then there is no reason to think

that it implicitly forbids a particular type of relief for a claim

outside its scope. For all these reasons, we conclude that the

waiver contained in § 702 of the APA subjects the Corps to

the plaintiffs’ common-law claims for declaratory and

injunctive relief.

C

The Corps and the District next contend that congressional

regulation has displaced as a matter of law the federal

common law on which the states rely. The district court

rejected this argument on the ground that Congress had not

done enough about the threat of invasive carp to qualify for

displacement of the federal common-law claim. The

defendants say this was error. As they see things, it is

enough that Congress has passed legislation to stop the carp

and that federal and state agencies are hard at work to

address the problem. Because the parties disagree about the

effect of American Electric Power and the way in which the

displacement analysis should proceed, we begin with a few

important principles.

The doctrine of displacement rests on the premise that

federal common law is subject to the paramount authority of

Congress. New Jersey v. New York, 283 U.S. 336, 348 (1931);

see also American Electric Power, 131 S. Ct. at 2537 (“[I]t is

primarily the office of Congress, not the federal courts, to

prescribe national policy in areas of special federal

interest.”). “‘[W]hen Congress addresses a question

previously governed by a decision rested on federal

common law . . . the need for such an unusual exercise of

law-making by federal courts disappears.’” American Electric

Power, 131 S. Ct. at 2537 (quoting Milwaukee II, 451 U.S. at

314). Displacementfocuses on the relation between Congress

and the federal courts – it is not a doctrine that is concerned
18 No. 10-3891

with the relation between the federal courts and the

executive branch. This is a distinction often neglected by

courts, as well as by the parties to this case. Whether federal

courts can or should play a role in the face of comprehensive

agency action is a critical issue, which we address below, but

executive action or lack thereof does not affect the

displacement analysis. See American Electric Power, 131 S. Ct.

2538-39 (rejecting the argument that an agency must have

taken action before common law is displaced and explaining

that the EPA’s outright refusal to regulate emissions would

not create a role for federal common law because “the

delegation [of regulatory authority from Congress to the

agency] is what displaces federal law”); Milwaukee II, 451

U.S. at 317-18, 324 n.18 (concluding that displacement had

occurred because “Congress . . . has occupied the field

through the establishment of a comprehensive regulatory

program supervised by an expert administrative agency,”

regardless of how thoroughly the agency has implemented

that program) (emphasis added). Congress’s decision to

assign a particular problem to an executive agency or its

description of an agency’s role in addressing a problem may

be evidence of displacement, but the ebb and flow of agency

action neither diminishes nor increases the role of federal

common law. The important displacement question is

whether Congress has provided a sufficient legislative

solution to the particularinterstate nuisance here to warrant

a conclusion that this legislation has occupied the field to the

exclusion of federal common law.

We readily concede that Congress has not been mute on

the subject of the carp, but that simply underscores the

critical question: how much congressional action is enough?

In their supplemental memoranda filed after American

Electric Power was decided, the defendants seize upon the

statement from the opinion that we quoted above – that “the

delegation is what displaces federal law.” 131 S. Ct. at 2538.

Their view is that all Congress must do to displace federal

law is to indicate its intention to delegate a particular

problem to an executive agency. They read American Electric
No. 10-3891 19

Power as an enlargement of whatever displacement doctrine

existed previously. But the defendants have taken the

Court’s statement out of context. The Court in that passage

was responding to an argument that an agency must have

acted pursuant to its statutory power before federal common

law is displaced. See id. at 2538-39. The Court explained that

this was not the case and that it is congressional action, not

executive action, that guides the displacement analysis. In so

ruling the Court did not establish a new test based solely on

Congress’s delegation of regulatory power; it simply pointed

out that delegation is one type of congressional action that

is evidence of displacement. “The test for whether

congressional legislation excludes the declaration of federal

common law,” the Court said, “is simply whetherthe statute

‘speak[s] directly to [the] question’ at issue.” Id. at 2537

(quoting Mobil Oil Corp. v. Higginbotham, 436 U.S. 618, 625

(1978), and citing Milwaukee II, 451 U.S. at 315, and County of

Oneida v. Oneida Indian Nation of N.Y., 470 U.S. 226, 236-37

(1985)). Importantly, while Congress must have spoken to

the particular question at issue, it is not necessary for us to

find the same manifest congressional purpose that we would

require in an analysis of whether Congress has preempted

state law. Id. at 2537.

Earlier federal nuisance cases provide additional insight

into the level of congressional action that is sufficient to

displace federal common law. In Milwaukee I, where Illinois

sued Milwaukee and other cities to stop them from dumping

sewage into Lake Michigan, the Court decided that the

federal common law of public nuisance had not been

displaced, despite the fact that Congress had by that time

“enacted numerous laws touching interstate waters.” 406

U.S. at 101-07. Laws that touched on the issue at hand were

not enough, and thus the common law action could move

forward. At the same time, however, the Court

foreshadowed that federal legislation “may in time pre-empt

the field of federal common law of nuisance.” Id. at 107. Six

months after Milwaukee I, Congress passed sweeping

amendments to the Federal Water Pollution Control Act
20 No. 10-3891

(FWPCA), and nine years after its first decision, the Court

decided in Milwaukee II that those amendments displaced

federal common law in the area. 451 U.S. at 317-18. The

Court viewed the amended statute as “a comprehensive

regulatory program supervised by an expert administrative

agency,” and it noted that under that regulatory program

“[e]very point source discharge is prohibited unless covered

by a permit.” Id. at 317-18. This permitting requirement

brought every potential interstate water polluter within

Congress’s administrative scheme; any discharge had to be

done with the permission of the EPA or a qualifying state

agency; and there were enforcement options available when

polluters failed to meet the conditions of permits that had

been issued. See id. at 310-11.

Mostrecently, American Electric Power held “that the Clean

Air Act and the EPA actions it authorizes displace any

federal common law right to seek abatement of

carbon-dioxide emissions from fossil-fuel fired power

plants.” 131 S. Ct. at 2537. The Court found it important that

the Clean Air Act requires the EPA to identify and establish

performance standards for all carbon-dioxide emitters; the

statute also “provides multiple avenues for enforcement,”

which include state agencies (operating under power

delegated by EPA), the EPA itself, criminal proceedings

against violators, and private enforcement in the event that

the EPA or the states fail to regulate emissions. If the EPA

has not acted, states and private parties may petition the

agency for a rulemaking, after which parties have a right to

review in federal court. Id. at 2537-38. The Court concluded

with the observation that “[t]he Act itself thus provides a

means to seek limits on emissions of carbon dioxide from

domestic power plants—the same reliefthe plaintiffs seek by

invoking federal common law. We see no room for a parallel

track.” Id. at 2538.

For better or for worse, congressional efforts to curb the

migration of invasive species, and of invasive carp in

particular, have yet to reach the level of detail one sees in the

air or water pollution schemes. In 1990, Congress passed the
No. 10-3891 21

Aquatic Nuisance Prevention and Control Act in an attempt

to stop the spread of zebra mussels and other nuisance

species. See 16 U.S.C. §§ 4701 et seq. That statute established

the Aquatic Nuisance Species Task Force and gave it the job

of studying invasive species and implementing a program

“to prevent introduction and dispersal of aquatic nuisance

species” in the United States. See id. § 4722. In 1996, the

National Invasive Species Act amended the 1990 law and

directed the Corps and the task force to “investigate and

identify environmentally sound methods for preventing and

reducing the dispersal of aquatic nuisance species between

the Great Lakes [basin] and the Mississippi River [basin]

through the Chicago River Ship and Sanitary Canal,”

including any methods that could be incorporated in the

normal operation of the CAWS. Id. § 4722(i)(3)(A). This

mandate led to the construction of an underwater electric

barrier in the Chicago Ship and Sanitary Canal. The barrier

sits just upstream of the point where the CAWS empties into

the Des Plaines River; it is designed to deter fish from

moving in either direction through the canal. In 2003 the

Corps, relying on the continuing authority given to the

Secretary of the Army in 33 U.S.C. § 2309a, began

construction of a second barrier next to the first. The barrier

projects received an additional influx of cash from the

District of Columbia Appropriations Act of 2005, Pub. L.

108-335, § 345, 118 Stat. 1352 (Oct. 18, 2004). In 2007,

Congress passed the Water Resources Development Act,

Pub. L. No. 110-114, § 3061(b)(1), 121 Stat. 1121 (Nov. 8,

2007), which allowed the Corps to upgrade its first barrier

and officially authorized the construction of the already-inprogress second barrier. Finally, the Corps received more

money to complete a third barrier as part of the American

Reinvestment and Recovery Act of 2009.

Sections 3061(b) and (d) of the Water Resources

Development Act of 2007, supra, instructed the Corps to

undertake two studies: a short-term examination of how the

electric barrier systems might more effectively stop invasive

species (this is the Efficacy Study, which so far consists of
22 No. 10-3891

four interim reports, see http://www.lrc.usace.army.mil/

AsianCarp/efficacy.htm); and a long-term study of how the

Mississippi and Great Lakes basins might be separated on a

more permanent basis (this is the Great Lakes and

Mississippi River Interbasin Study or “GLMRIS,” see

http://glmris.anl.gov). In an appropriations bill forfiscal year

2009, Congress provided that “the Secretary of the Army

shall implement measures recommended in the efficacy

study, or provided in interim reports, authorized under

section 3061 of the Water Resources Development Act of

2007 . . . with such modifications or emergency measures as

the Secretary of the Army determines to be appropriate, to

prevent aquatic nuisance species from bypassing the

Chicago Sanitary and Ship Canal Dispersal Barrier Project

referred to in that section and to prevent aquatic nuisance

species from dispersing into the Great Lakes.” Energy and

Water Development and Related Agencies Appropriations

Act 2010, Pub. L. No. 111-85, § 126, 123 Stat. 2845, 2853 (Oct.

28, 2009). This authority – referred to informally as the

Section 126 power — is set to expire on September 30, 2011.

Department of Defense and Full-Year Continuing

Appropriations Act 2011, Pub. L. No. 112-10, §§ 1101(a)(2),

1104, 1106, 125 Stat. 38, 103 (Apr. 15, 2011). Add to these

measures the appropriation of funds so that the Corps can

ensure proper operation of the CAWS,e.g., Pub. L. No. 98-63,

97 Stat. 301, 311 (July 30, 1983); Pub. L. No. 97-88 § 107, 95

Stat. 1135, 1137 (Dec. 4, 1981); Pub. L. No. 79-525, 60 Stat.

634, 636 (July 24, 1946), and one has the whole of Congress’s

efforts to stop invasive species from moving through the

CAWS. Recent legislative proposals targeted at halting

invasive carp have failed in both Houses. E.g., Close All

Routes and Prevent Asian Carp Today Act of 2010 (CARP

ACT), H.R. 4472, S. 2946.

Although this legislation demonstrates that Congress is

aware of the problem of invasive species generally, and carp

in particular, it falls far short of the mark set by the Clean

Air Act or the Federal Water Pollution Control Act.

Congress has not passed any substantive statute that speaks
No. 10-3891 23

directly to the interstate nuisance about which the states are

complaining. Most of the laws that we have summarized

appropriate funds to the Corps for routine maintenance of

the CAWS or for the electric barrier project. Apart from

requiring the construction of these barriers and giving the

Secretary of the Army temporary power to implement

various recommendations, Congress has ordered agencies

(or, more commonly, informal task forces composed of

various executive actors) only to study the invasive species

problem and propose solutions. Beyond that, neither the

Corps nor any other agency has been empowered actively to

regulate the problem of invasive carp, and Congress has not

required any agency to establish a single standard to deal

with the problem or to take any other action. The narrow

delegation that has taken place bears little resemblance to

the regulatory power that the EPA wields under the Clean

Air Act. Tellingly, Congress has not provided any

enforcement mechanism or recourse for any entity or party

negatively affected by the carp, and there is certainly no

recourse to the courts under the minimal scheme that has

been established. The district court was correct that the

current state of congressional regulation is much closer to

the situation examined in Milwaukee I – and perhaps even

less extensive than that – than the regimes reviewed in

Milwaukee II or American Electric Power.

D

With these important preliminary questions out of the

way, we are at last ready to consider whether the plaintiff

states have presented enough evidence in support of their

nuisance claim to establish that they are likely to succeed on

the merits. The district court thought that the states failed to

demonstrate more than a minimal chance of success. Before

this court, the states contend that the district court

misunderstood the elements of public nuisance. They point

to the district judge’s statement that the tort “contemplates

an active – or, at least, an imminent – threat of injury” as

evidence of that error. In their view, all they must show to

win final relief in a trial on the merits is that there is a
24 No. 10-3891

“significant threat” that the nuisance will occur. This is a

distinction without a difference; the district court correctly

understood the law of public nuisance. Nonetheless, for

different reasons we think that the district judge may have

underestimated the states’ likelihood of success. We will

elaborate on this point after a brief review of the governing

law.

1

The district court began with the definition of public

nuisance found in the Restatement (Second) of Torts, which has

been a common reference point for courts considering cases

arising under federal common law. See Connecticut v.

American Electric Power Co., Inc., 582 F.3d 309, 351 & n.28 (2d

Cir. 2009), rev’d on other grounds, American Electric Power, 131

S. Ct. 2527 (explaining that “[t]he Restatement definition of

public nuisance has . . . been used in . . . federal cases

involving the federal common law of nuisance . . . and the

Restatement principles have served as the backbone of state

nuisance law”). The Restatement provides that “A public

nuisance is an unreasonable interference with a right

common to the general public,” RESTATEMENT (SECOND) OF

TORTS § 821B(1), and it goes on to explain that conduct meets

this standard when it interferes significantly with the public

health, safety, peace, comfort, or convenience, id. §

821B(2)(a). We described above the reasons why the federal

common law of public nuisance is available to redress the

type of harm that the states have alleged. And all sides agree

that if invasive carp were to achieve a sustainable

population in the Great Lakes, the environmental and

economic impact would qualify as an unreasonable

interference with a public right. As the district court noted,

the Corps and other agencies have repeatedly and publicly

acknowledged the seriousness of the problem. The Corps,

for example, has said that invasive carp “have the potential

to damage the Great Lakes and confluent large riverine

ecosystems,” and that it regards “[t]he prevention of an

inter-basin transfer of bighead and silver carp from the

Illinois River to Lake Michigan [as] paramount in avoiding
No. 10-3891 25

ecologic and economic disaster.” As a result, the central

question on the merits of the states’ public nuisance claim

will be whether the harm that the states have described is

sufficiently close to occurring that the courts should order

the defendants to take some new action that will be effective

to abate the public nuisance. We stress at the outset an

important point to which we will return: this question is one

that will be resolved after a full trial on the merits, rather

than at this preliminary stage of the case.

A court may grant equitable relief to abate a public

nuisance that is occurring or to stop a threatened nuisance

from arising. See Tennessee Copper, 206 U.S. at 238-39

(requiring the plaintiff to show that a defendant’s actions

“cause and threaten damage”).In Missouri v.Illinois, 200 U.S.

at 518, the Court wrote that the threatened harm underlying

the nuisance claim “must be shown to be real and

immediate.” We have read the Court’s cases to say that

“[t]he elements of a claim based on the federal common law

of nuisance are simply that the defendant is carrying on an

activity that is causing an injury or significant threat of

injury to some cognizable interest of the complainant,”

Illinois v. City of Milwaukee, 599 F.2d 151, 165 (7th Cir. 1979),

rev’d on other grounds, Milwaukee II, 451 U.S. 304. Additional

statements about averting threatened nuisances appear in

the Restatement, see RESTATEMENT (SECOND) TORTS § 821B

cmt. (i) (“[F]or damages to be awarded [in public nuisance

cases] significant harm must have been actually incurred,

while for an injunction harm need only be threatened and

need not actually have been sustained at all.”); id. § 821F

cmt. (b) (“[E]ither a public or a private nuisance may be

enjoined because harm is threatened that would be

significant if it occurred.”), and in other treatises, see, e.g., 5

J. POMEROY, A TREATISE ON EQUITY JURISPRUDENCE AND

EQUITABLE REMEDIES, § 1937 (§ 523), at 4398 (2d ed. 1919)

(noting that while “a mere possibility of a future nuisance

will not support an injunction,” relief will be warranted

when “the risk of its happening is greater than a reasonable

man would incur”).
26 No. 10-3891

The plaintiffs believe that the district court’s “imminent

threat” requirement is inconsistent with these principles, but

we do not share that view. The district court reproduced

verbatim the elements of the claim as we described them in

Illinois v. City of Milwaukee, supra. Its discussion of

“immediacy” did nothing more than flesh out the Court’s

requirement of a “real and immediate” threat in public

nuisance cases. There is no meaningful legal difference for

purposes of the ultimate resolution of a public nuisance

claim between a threatened nuisance that is “imminent” and

one that is “immediate,” “significant,” “real,” an

“unreasonable risk,” or anything similar. The job of a court

considering the merits of a public nuisance claim is simply

to determine whether the activity complained of is a

nuisance and, if so, whether it is sufficiently close to

occurring that equitable relief is necessary to prevent it from

happening.

2

We part company with the district court when it comes to

the assessment of the states’ likelihood of success on the

merits. Here we think it critical to bear in mind the

difference between preliminary or interim relief, on the one

hand, and permanentrelief, on the other. The principles that

we just reviewed relate to the ultimate outcome of a public

nuisance proceeding. This case has not yet reached that

stage, and one consequence of its preliminary posture is that

the states were not required to prove that they will

ultimately win on the merits in order to secure preliminary

relief.

“The propriety of preliminary relief and resolution of the

merits are of course significantly different issues.” Parents

Involved in Cmty. Sch. v. Seattle Sch. Dist. No. 1, 551 U.S. 701,

721 n.10 (2007) (internal quotation marks omitted). This is

the reason why findings made at the preliminary injunction

stage do not bind the district court as the case progresses. Cf.

Guaranty Bank v. Chubb Corp., 538 F.3d 587, 591 (7th Cir.

2008). The most significant difference between the
No. 10-3891 27

preliminary injunction phase and the merits phase is that a

plaintiff in the former position needs only to show “a

likelihood of success on the merits rather than actual

success.” Amoco Prod. Co. v. Village of Gambell, 480 U.S. 531,

546 n.12 (1987); cf. Chathas v. Local 134 Int’l Bhd. of Elec.

Workers, 233 F.3d 508, 513 (7th Cir. 2000) (“A plaintiff cannot

obtain a permanent injunction merely on a showing that he

is likely to win when and if the merits are adjudicated.”). In

some cases, it is necessary to expedite an ultimate decision,

and so courts sometimes consolidate the preliminary

injunction hearing with the trial on the merits. See FED. R.

CIV. P. 65(a)(2). But where such consolidation has not taken

place – and it has not here – and the question is the

propriety of preliminary relief, the Supreme Court has

warned against “improperly equat[ing] ‘likelihood of

success’ with ‘success’ . . . .” University of Texas v. Camenisch,

451 U.S. 390, 394 (1981); see also Meridian Mut. Ins. Co. v.

Meridian Ins. Group, Inc., 128 F.3d 1111, 1119 (7th Cir. 1997).

This is in keeping with the often-repeated rule that the

threshold for establishing likelihood of success is low. E.g.,

Cooper v. Salazar, 196 F.3d 809, 813 (7th Cir. 1999); Brunswick

Corp. v. Jones, 784 F.2d 271, 275 (7th Cir. 1986).

We are concerned that the district court here may have

lost sight of this distinction. By applying directly the law of

public nuisance, the judge seems to have required the

plaintiff states actually to show that they were entitled to

permanent injunctive relief during the preliminary

injunction hearing. The court concluded its discussion of the

threat posed by invasive carp, for example, by saying that

the states “ha[d] not made a convincing case” that the fish

had pushed into the CAWS in significant numbers; and it

said that the plaintiffs had not “shown that the fish [are]

anywhere near . . . establishing a population in Lake

Michigan.” Because the states had not yet shown that the

threat of nuisance was great enough in the final analysis to

warrant an injunction to abate it, the district court seems to

have assumed that they had also failed to show enough to

obtain preliminary relief. To demonstrate the requisite
28 No. 10-3891

likelihood of success, however, the states needed only to

present a claim plausible enough that (if the other

preliminary injunction factors cut in their favor) the entry of

a preliminary injunction would be an appropriate step. The

preliminary injunction, after all, is often seen as a way to

maintain the status quo until merits issues can be resolved at

trial. By moving too quickly to the underlying merits, the

district court required too much of the plaintiffs and,

correspondingly, gave too little weight to the strength of

their claim at this stage of the case.

3

We also question the inferences drawn by the district court

from the facts that it so carefully found after evaluating five

days of hearings, which included the testimony of expert

witnesses and volumes of written materials on complex

scientific and engineering issues. There is very little to

criticize about the court’s factual findings themselves. For

instance, the district judge’s decision to admit the expert

testimony of Dr. David Lodge, who has been hired by the

Corps and who testified for the states at the preliminary

injunction hearing about his efforts to track invasive carp

through the use of environmental DNA (eDNA) testing,

reflects a proper application of Federal Rule of Evidence 702.

(We agree that any lack of peer review of Dr. Lodge’s work

would go to the weight of his testimony, not to the court’s

ability to consider it. Moreover, the situation will be

different at the merits phase, given Dr. Lodge’s recent

publication of his research. See Christopher L. Jerde,

Andrew R. Mahon, W. Lindsay Chadderton & David M.

Lodge, “Sight Unseen” Detection of Rare Aquatic Species Using

Environmental DNA, 4 Conservation Letters 150 (April/May

2011).) We also see nothing to criticize in the district court’s

assessment that the electric barriers built by the Corps near

the intersection of the Chicago Sanitary and Ship Canal and

the Des Plaines River seem to have at least some deterrent

effect on the movement of invasive carp toward the Great

Lakes. In addition, we consider it significant, as the district

judge did, that efforts to detect carp by techniques including
No. 10-3891 29

netting, so-called electrofishing, and rotenone poisoning,

have led to few signs of the carp.

Along the same lines, the district court was right to take

into account the results of eDNA testing. Despite its

skepticism about the reliability of the technique and its

concern that the state of eDNA science “did not permit a

reasonable inference that live Asian carp are in the [CAWS]

. . . in numbers that present an imminent threat,” the court

acknowledged that the eDNA evidence lent some support to

the conclusion that there may be invasive carp above (i.e.

lakeside of) the Corps’s electric barriers. Although we are

less skeptical of the science than the district court, we too

believe that caution in drawing inferences from the existence

of carp DNA in the water is warranted. The eDNA

technique, which tests water samples for markers matching

a particular species, has a number of shortcomings: it is

difficult, if not impossible, to know definitively whether a

positive result signals a living specimen above the barrier

(DNA may be shed by a dead or distant fish); a positive test

does not reveal the number of live fish; and negative results

do not necessarily signal the absence of carp. Efforts to

corroborate eDNA results with traditional methods of

capturing fish have not been successful thus far. On the

other hand, the evidence is worth something. The eDNA

technique detects carp when the fish are present in small

numbers and in situations where the other fishing methods

we described above might scare them away or simply miss

them, and the large number of negative test results make

sense given the sensitivity of the technique. In addition, the

Corps and other agencies have voted with their feet: they

have been using eDNA tests to manage the invasive carp

crisis, and they have said that this testing will continue.

(This is undoubtedly why the private intervenor-defendants

are the primary critics of this methodology.) If the tests are

good enough for expert agencies, it is hard to see why we

should flatly forbid their consideration. A January 2011

report on eDNA sampling conducted in 2010 showed

positive eDNA results in approximately a dozen locations
30 No. 10-3891

throughout the CAWS, and experts have opined that these

results indicate the presence of carp at multiple locations in

the CAWS. On July 29, 2011, federal officials announced that

they would begin daily efforts to find invasive carp around

Lake Calumet, after multiple rounds of testing revealed carp

DNA in that area. See Asian Carp Regional Coordinating

C o m m itt e e , P r e s s Re l e a s e , Ju ly 2 9 , 2 0 1 1 ,

http://asiancarp.org/news/asian-carp-regional-coordinatingcommittee-to-begin-intensive-monitoring-in-lake-calumetin-response-to-environmental-dna-results; TammyWebber,

Feds to Step Up Hunt for Asian Carp Near Chicago, Chicago

Tribune, July 29, 2011. The district court thought that this

evidence, in combination with the discovery of two invasive

carp specimens (one dead and one living) in the CAWS,

supported a theory that invasive carp are present in the

CAWS in “low numbers.” This conclusion was reasonable.

The carp may even be present in greater numbers, but for

present purposes we do not need any more precision.

Our greatest hesitation with respect to the district court’s

findings is over its conclusion that “it is far from certain that

Asian carp can survive and reproduce in the Great Lakes.”

Given the record that was before Judge Dow, this prediction

may have been sound at the time he ruled. The situation has

been evolving rapidly since the preliminary injunction

hearing, however, and so we think it worth mentioning that

the newest publicly available evidence suggests that when

and if the time comes, the carp are unlikely to have trouble

establishing themselves in the Great Lakes. Before the

district court there was testimony reflecting great

uncertainty about how easily the carp could live and

reproduce in this new habitat. A species typically requires

multiple introductions before it takes root in a new

ecosystem, and there has been a substantial debate,reflected

in the literature, about whether the food supply and other

features of the Great Lakes could support the carp. See

generally Sandral L. Cooke & Walter R. Hill, Can FilterFeeding Asian Carp Invade the Laurentian Great Lakes? A

Bioenergetic Modelling Exercise, 55 Freshwater Biology 2138
No. 10-3891 31

(2010); Cynthia S. Kolar & David M. Lodge, Ecological

Predictions and Risk Assessment for Alien Fishes in North

America, 298 Science 1233 (2002). On April 28, 2011, however,

the Obama Administration presented two pieces of what it

called “bad news” at a meeting in Chicago on invasive carp:

first, it said that while it was once thought that the carp

could not establish breeding populations in Lake Michigan

because of the low levels of plankton (the carp’s normal food

source) in the water, new evidence suggests that the fish will

happily switch from eating plankton to consuming the green

algae that now covers the lake floor (thanks to another

invasive species, the zebra mussel); and (2) while experts

had thought the carp need coastal rivers between 30 and 60

miles long to spawn, it turns out they can make do with

much shorter breeding grounds. See,e.g., Asian Carp Possibly

Hardier than Once Thought, Chicago Tribune, Apr. 28, 2011.

At this point, therefore, we must assume that once in the

Great Lakes, the invasive carp would make it their home.

We need not explore the factual record further. As we

have said, our review of the district court’s findings is

deferential, and we see nothing that demands correction.

The critical point is that this record is not a static thing. The

district court will undoubtedly have more evidence before

it when it is time to rule on the request for a permanent

injunction, and we are confident that the court will keep its

mind open to the implications of any new information. For

purposes of assessing the need for preliminary relief, the

court relied on its findings that at best a limited number of

invasive carp were present in the CAWS and its observation

that the so-called invasion front was approximately 30 miles

downstream of the CAWS (60 miles from Lake Michigan) as

of the spring of 2009. On this basis, it reached the conclusion

that while the potential for damage to the Great Lakes is

high, the problem had not advanced far enough to present

a threat to the plaintiff states. From that it drew the

conclusion that the states had shown little likelihood of

success on the merits.

It is that final step that gives us trouble. As the district
32 No. 10-3891

court rightly noted, the magnitude of the potential harm

here is tremendous, and the risk that this harm will come to

pass may be growing with every passing day. (It certainly

has grown since the ill-fated day around 1970 when the carp

escaped from various aquaculture facilities and began their

march up the Mississippi River. See generally Wisconsin

Dep’t of Nat. Res., Bighead and Silver Carp

(Hypophtha lmi chthys no bilis and H. mo litrix),

http://dnr.wi.gov/invasives/fact/asian_carp.htm.) Given the

magnitude of the harm, we are inclined to give the benefit of

the doubt to the states on the question whether they have

shown enough of a risk of nuisance to satisfy the likelihoodof-success requirement at this preliminary stage. See Van De

Sande v. Van De Sande, 431 F.3d 567, 570 (7th Cir. 2005) (“The

gravity of a risk involves not only the probability of harm,

but also the magnitude of the harm if the probability

materializes.”) (citing United States v. Carroll Towing Co., 159

F.2d 169, 173 (2d Cir. 1947)). In addition, the nature of the

threat – an ecological harm – suggests that a broader

perspective on the problem might be necessary. It is hard to

see 60 miles of separation between the carp invasion front

and the Great Lakes (and remember this was the estimated

distance more than two years ago) as a particularly safe

margin, even with functioning electric barriers to deter fish

and efforts to reduce propagule pressure (the volume of

invasive carp in the water downstream of the front). It is

especially chilling to recall that in just 40 years the fish have

migrated all the way from the lower Mississippi River to

within striking distance of the lakes and have come to

dominate the ecosystem in the process. Commercial

harvesting of carp in the Mississippi basin increased from

just over five tons to 55 tons in the three-year period from

1994 to 1997; there is evidence that by 1999 invasive carp

made up 97% of the Mississippi’s biomass; and as of 2007

commercial fishers were catching 12 tons of invasive carp

each day. These numbers are sobering even apart from the

hints that some of the fish may have made it into the CAWS

already.
No. 10-3891 33

In our view, the proper inference to draw from the

evidence is that invasive carp are knocking on the door to

the Great Lakes. We need not wait to see fish being pulled

from the mouth of the Chicago River every day before

concluding that a threat of a nuisance exists. It is enough

that the threat is substantial and that it may be increasing

with each day that passes. Unlike many nuisances that can

be eliminated after they are discovered, this one in all

likelihood cannot be. The fact that it would be impossible to

un-ring the bell in this case is another reason to be more

open to a conclusion that the threat is real. In our view, the

plaintiff states presented enough evidence to establish a

good or even substantial likelihood of success on the merits

of their public nuisance claim.

III

Before moving on to the other preliminary injunction

factors, there are some particular questions about the APA

claim against the Corps that we must address. We turn

again to § 702 of the APA, which authorizes a suit by “[a]

person suffering legal wrong because of agency action, or

adversely affected or aggrieved by agency action within the

meaning of a relevant statute.” 5 U.S.C. § 702. A reviewing

court is required to “compel agency action unlawfully

withheld or unseasonably delayed,” 5 U.S.C. § 706(1), and to

“set aside agency action . . . found to be . . . arbitrary,

capricious, an abuse of discretion, or otherwise not in

accordance with law,” id. § 706(2)(A). The states do not ask

us to compel the Corps to take action, at least as far as §

706(1) is concerned. Norton v. Southern Utah Wilderness

Alliance, 542 U.S. 55, 64 (2004), explains that “a claim under

§ 706(1) can proceed only where a plaintiff asserts that an

agency failed to take a discrete agency action that it is required

to take”; the states have named no action that they think the

agency is required to take. We understand the states’

argument as a request to set aside agency action that they

regard as unlawful within the meaning of § 706(2)(A).
34 No. 10-3891

The obvious starting point is to identify the final Corps

action that the states assert has affected them. See 5 U.S.C.

§ 704; Lujan v. National Wildlife Fed’n, 497 U.S. 871, 882 (1990).

The states contend that five such actions fit the bill. They say

that the Corps’s (1) operation of the CAWS in a manner that

will let invasive carp into Lake Michigan, (2) reliance on

ineffective electric barriers, (3) use of locks in areas where

living and dead carp have been found, (4) denial of the

states’requests for additionalrelief, and (5) implementation

of recommendations contained in the Corps’s third interim

report (which is part of the Efficacy Study we discussed in

connection with our analysis of displacement, supra) are all

final agency actions. The district court equivocated on the

issue, but it seems to have agreed with the states in the end.

There is a good chance that most of the “actions” named

by the states are not “final agency actions” for purposes of

the APA. “Agency action” is defined as “the whole or a part

of an agency rule, order, license, sanction, relief or the

equivalent or denial thereof, or failure to act,” 5 U.S.C. §

551(13). The Supreme Court has explained that these

categories all “involve circumscribed, discrete agency

actions,” Norton, 542 U.S. at 62. Agency action is “final”

when it marks the consummation of the agency’s

decisionmaking process and determines legal rights or

obligations. Bennett v. Spear, 520 U.S. 154, 177-78 (1997); see

also Western Illinois Home Health Care, Inc. v. Herman, 150

F.3d 659, 662 (7th Cir. 1998) (citing Franklin v. Massachusetts,

505 U.S. 788 (1992), for the proposition that “[t]he core

question is whether the agency has completed its

decisionmaking process, and whether the result of that

process is one that will directly affect the parties”). Applying

these standards, we cannot see why any of the “actions” that

are numbered 1 through 4 on the states’ list of complaints

above should be considered final agency action. Most of the

four “actions” are not discrete at all; and those that might be

so classified do not represent the final outcome of any

decisionmaking process by the Corps. The Corps’s effort to

implement its third interim report – which recommended
No. 10-3891 35

the installation of screens over two gates that control water

flow between the CAWS and Lake Michigan but which

otherwise called for normal operation of lake-facing locks –

is the only activity that may be suitable for an APA

challenge. We need not evaluate that claim in any detail,

however, because it is part of the states’ larger request for

relief based on the common law of public nuisance.

Two types of plaintiffs are given a right of review in § 702:

those suffering a “legal wrong,” and those “adversely

affected or aggrieved by agency action within the meaning

of a relevant statute.” In their briefs in this court, the states

have not pointed to a single statute against which one might

judge the Corps’s behavior. (This is not surprising, given the

dearth of pertinent federal legislation that we discussed in

connection with displacement.) The Corps submits that this

means that the states have no APA claim; the states respond

their APA claim is “free-standing.” Neither answer is

satisfactory. We know that the states have not alleged that

the Corps’s actions failed to comply with some statutory

provision, and so they must instead be asserting that they

have suffered a “legal wrong” because of those actions. The

only legal wrong that comes to mind, however, is the

infliction of a common-law public nuisance. See Lujan, 497

U.S. at 883 (distinguishing between legal wrongs and the

failure of an agency to comply with a statutory provision);

Tennessee Electric Power Co. v. Tennessee Valley Authority, 306

U.S. 118, 137 (1939) (explaining that “legal wrong” includes

tortious invasions and interferences with property and

contractual rights). See generally Antonin Scalia, The

Doctrine of Standing as an Essential Element of the Separation of

Powers, 17 SUFFOLKU.L.REV. 881, 887-890 (1983) (discussing

the use of the term “legal wrong” in the APA and explaining

that it “could only mean a wrong already cognizable in the

courts”). The result is that the states’ APA claim against the

Corps sinks or swims (so to speak) with its public nuisance

theory. Because they are indistinguishable, we address only

the latter from this point on.
36 No. 10-3891

IV

To satisfy the second threshold requirement for

preliminary injunctive relief, the states must establish that

irreparable harm is likely without an injunction. Judge v.

Quinn, 612 F.3d 537, 557 (7th Cir. 2010). In the district court’s

view, this issue was the same as the question whether the

states had shown a likelihood of success on the merits of

their public nuisance claim. The states contend that it was

error to conflate these inquiries. They are right. In this case,

for example, the likelihood of success on the merits focuses

on the threat of a nuisance, while the irreparable harm is

concerned with the ability to correct that nuisance if it is

created. Not every nuisance will give rise to irreparable

harm. These two steps of the preliminary injunction analysis

thus play different roles. The likelihood of success on the

merits is an early measurement of the quality of the

underlying lawsuit, while the likelihood of irreparable harm

takes into account how urgent the need for equitable relief

really is. Typically, these lines of inquiry will have some

overlap, but they should not be treated as the same. With

that in mind, we realize that the same evidence will inform

both steps of the preliminary injunction analysis in this case.

As long as the distinctions we have just mentioned remain

clear, there is no harm in analyzing all of the evidence once

rather than twice. As a result, the states’ criticism of the

district court is largely academic and provides no reason to

reverse that court’s decision.

Putting theory to one side, we have very little trouble

concluding that the environmental and economic harm that

the states have shown might come to pass would be

genuinely irreparable if it did occur. The district court

implied that this was the case when it discussed the

magnitude of the potential harm. Last year in Supreme

Court filings related to this litigation, the United States

explained in a memorandum that it agreed with Michigan

“that allowing a reproducing population of Asian carp to

establish itself in Lake Michigan likely would be an

irreparable injury.” Memorandum in Opposition of the
No. 10-3891 37

United States, at 43, Original Nos. 1, 2, and 3,

http://w w w . supreme court.gov/SpecMas tRpt/US_

Memorandum_in_Opposition.pdf; see also id. at 47 (calling

the harm “grave and irreparable”). All of the other parties

seem to agree with this view. (To the extent that the

defendants argue that there is no irreparable harm because

the carp cannot establish a breeding population in Lake

Michigan, they are avoiding the key question: what if the

fish did establish a successful breeding group?) This nearunanimity on the question ofirreparable injury makes sense.

“Environmental injury, by its nature, can seldom be

adequately remedied by money damages and is often

permanent or at least of long duration, i.e., irreparable.”

Amoco Prod., 480 U.S. at 545; Sierra Club v. Franklin County

Power of Illinois, LLC, 546 F.3d 918, 936 (7th Cir. 2008). Harms

like those the states allege here are irreparable because they

are difficult – if not impossible – to reverse. See Hollingsworth

v. Perry, 130 S. Ct. 705, 712 (2010) (per curiam).

For preliminary relief to be granted, the irreparable harm

must also be likely. That is, there must be more than a mere

possibility that the harm will come to pass, Winter, 555 U.S.

at 21-23, but the alleged harm need not be occurring or be

certain to occur before a court may grant relief, United States

v. W.T. Grant Co., 345 U.S. 629, 633 (1953); United States v.

Oregon State Med. Soc’y, 343 U.S. 326, 333 (1952); Bath Indus.,

Inc. v. Blot, 427 F.2d 97, 111 (7th Cir. 1970). Commentators

describe the required level of certainty this way: “[A]

preliminary injunction will not be issued simply to prevent

the possibility of some remote future injury. A presently

existing actual threat must be shown. However, the injury

need not have been inflicted when application is made or be

certain to occur.” 11A CHARLES ALAN WRIGHT, ET AL.,

FEDERALPRACTICEAND PROCEDURE§ 2948.1, at 154-55 (2d ed.

1995). Because the district court analyzed likelihood of

success on the merits at the same time as it assessed the

danger of irreparable harm, all of the reservations we had

about the inferences drawn by the district court in the

former context apply with equal force here.
38 No. 10-3891

As we have already pointed out, no one knows whether

this irreparable harm will come to pass. The intense factual

dispute we are witnessing here about the rate at which

invasive carp are progressing makes evaluating its

likelihood even more tricky. In our view, the district court

required a level of proof too close to certainty when it

assessed the danger of invasive carp escaping into Lake

Michigan. Given the dire nature of the harm posed by the

carp and their close proximity to the CAWS, we again will

give the plaintiff states the benefit of the doubt. Just as they

produced enough evidence to establish a likelihood of

success on the merits warranting injunctive relief, so too

have they shown, to the degree necessary for preliminary

relief, that it is likely that irreparable harm will come to pass.

This sets the stage for the dispositive issue: how must the

harms the states have identified be balanced against those

that the defendants will suffer should an injunction be

granted?

V

The balancing process to which we now turn is a classic

part of any preliminary injunction inquiry. See Winter, 555

U.S. at 24 (“A preliminary injunction is an extraordinary

remedy never awarded as of right. In each case, courts must

balance the competing claims of injury and must consider

the effect on each party of the granting or withholding of the

requested relief.”) (internal quotation marks and citations

omitted). How much of the danger forecast by the states

would be avoided by the particular injunction they have

asked for? And what harm would the injunction impose on

the defendants? Typically, after we balance these partyspecific equities, we evaluate whether the injunction would

advance orimpede the public interest. See,e.g., Ferrell v. U.S.

Dep't of Hous. and Urban Dev., 186 F.3d 805, 811 (7th Cir.

1999). That additional analysis is not necessary in this case,

however, because the parties themselves, with the exception

of two intervenors, are governmental entities that represent
No. 10-3891 39

the interests of the public.

When it appears that preliminary relief may be

burdensome, the Supreme Court has instructed courts to be

careful as they balance the competing interests. Winter, 555

U.S. at 27; see also Kartman v. State Farm Mut. Auto. Ins. Co.,

634 F.3d 883, 892 (7th Cir. 2011). In light of the multifarious

ideas the states have for an injunction in this case, there can

be no doubt that caution must be our word of the day. Even

if a plaintiff’s suit appears to have merit, an injunction

should not necessarily issue if the harm to the defendant

would substantially outweigh the benefit to the plaintiff.

MacDonald v. Chicago Park Dist., 132 F.3d 355, 357 (7th Cir.

1997).

In the end we conclude that a preliminary injunction

would cause significantly more harm that it would prevent.

We reach this result for two reasons, which we summarize

here before explaining the balance of harms in more detail.

First, there are a number of problems with various line items

in the plaintiffs’ proposed package of relief. Taken together,

these problems leave us doubting whether the proposed

injunction would reduce by a significant amount the risk

that invasive carp will gain a foothold in the Great Lakes

between now and the time that a full trial on the merits is

completed. It is clear, on the other side, that the requested

measures would impose substantial costs on the defendants

and the public interests they represent, as well as added

expenses for commerce, recreation, and tourism. Second, as

circumstances currently stand, there is a more fundamental

reason that the states’ requested injunction is unlikely to

prevent much harm and actually may impose costs. The

courts would not be acting alone. As we have explained,

there is a powerful array of expert federal and state actors

that are engaged in a monumental effort to stop invasive

carp from entering the Great Lakes. The last thing we need

is an injunction operating at cross-purposes with their

efforts or imposing needless transactional costs that divert

scarce resources from science to bureaucracy. Furthermore,

from an institutional perspective courts are comparatively
40 No. 10-3891

ill situated to solve this type of problem. The balance of

harms favors the defendants and the public interests they

represent to such an extent that we conclude that the district

court’s decision to deny preliminary relief was not an abuse

of discretion.

A

1

It is best to begin by trying to understand precisely what

preliminary relief the states would like. As the district court

noted, their request has evolved as the case has moved

forward. Indeed, their position has shifted even between

their opening brief in this court and oral argument. The

moving nature of the target complicates our job of

evaluating the propriety of injunctive relief. Moreover, their

request has been phrased at a high level of generality. They

have given us the broad strokes of additional steps they

would like us to order the defendants to take, but they have

not furnished many details about how this relief would be

implemented, on what schedule, at what cost, and on whose

nickel. From time to time the states urge that the injunctive

measures should be “consistent with public health and

safety,” but they do not say what precisely that means. This

vagueness is unhelpful; it stands as an obstacle to the entry

of an injunction that will satisfy Federal Rule of Civil

Procedure 65(d). See PMC, Inc. v. Sherwin-Williams Co., 151

F.3d 610, 619-20 (7th Cir. 1998); see also Patriot Homes, Inc. v.

Forest River Hous., Inc., 512 F.3d 412, 414-15 (7th Cir. 2008).

When a plaintiff seeks relief of the type the states ask for

here, we have required a more specific plan about the

measures to be taken and the costs of implementing those

measures. See Jordan v. Wolke, 593 F.2d 772, 774-75 (7th Cir.

1978).

At this time, it is our understanding that the states believe

that they are entitled to a preliminary injunction that would

require the defendants to take these five steps:

a. Closing the Locks. Close and stop operating the locks at
No. 10-3891 41

the Chicago River Controlling Works (the Controlling

Works) and the O’Brien Lock and Dam (O’Brien), which

sit at two of the five points of contact between the CAWS

and Lake Michigan;

b. Screens over Sluice Gates. Install nine additional screens

over sluice gates that are used to control water flow

between the CAWS and the lake at the Controlling Works,

O’Brien, and the Wilmette Pumping Station, a third

contact point with Lake Michigan;

c. Block Nets in the Rivers. Place block nets to stop fish in

the Little Calumet River, which connects the CAWS to the

lake at the Burns Small Boat Harbor in Indiana, and if

necessary in the Grand Calumet River, which runs

between the CAWS and the Indiana Harbor and Canal

(Burns Harbor and Indiana Harbor are last of the five

contact points between the CAWS and Lake Michigan);

d. Rotenone Poisoning. Use rotenone to poison fish in the

CAWS, especially in areas north of O’Brien.

e. Accelerating GLMRIS. Finish the part of the Great Lakes

and Mississippi River Interbasin Study that relates to the

CAWS, which Congress called for in the Water Resources

Development Act of 2007, within 18 months.

The states have made two additional requests that do not

require discussion. They say that the defendants should use

the best methods to stop, capture, and kill carp that are

present in the CAWS. We see this as a more general

statement of the specific measures we have just outlined. In

addition, the states want the defendants to continue using

monitoring techniques, including eDNA testing, to search

for invasive carp. But the Corps and the other agencies

working on this problem are continuing eDNA monitoring

efforts. In July 2011, for example, three rounds of positive

eDNA testing results led to a four-day hunt forinvasive carp

(none was found). This request asks for steps already being

taken, and so we will not discuss it further.

2
42 No. 10-3891

Before we discuss the harm and benefit of the preliminary

relief the states request, we must point out an error in the

states’ view of how the harms should be weighed. The states

say that any harm the defendants might suffer because of

the injunction pales “in comparison to the grave and truly

irreparable harm that will occur if Asian carp establish a

breeding population in the Great Lakes.” But that is not the

correct measure of the harm avoided by the states’ proposed

injunction. The states assume, without providing much

explanation, that preliminary relief would stop invasive carp

from ever reaching the Great Lakes. While that may be the

effect that a perfectly designed permanent injunction would

have, it is not an accurate measure of the harm that would

be avoided by the states’ proposed preliminary injunction.

At this early point, the question is to what extent would the

proposed measures decrease the risk of invasive carp

establishing themselves in the Great Lakes between now and

when the litigation concludes? Stepping back from the

subject matter of this litigation, we note that in addition to

the CAWS, the Corps has identified a total of 18 places in

Minnesota, Wisconsin, Indiana, Ohio, and New York where

invasive carp could move from the Mississippi basin into the

Great Lakes. These pathways outside of the CAWS

necessarily reduce the likelihood that the states’ preliminary

injunction will prevent carp from establishing themselves in

the Great Lakes, because the states’ proposed measures say

nothing about these alternate routes. Even focusing

exclusively on the CAWS, the states overlook similar

limitations inherent in the steps they are proposing –

limitations that would reduce the effectiveness of

preliminary relief, as we now explain.

a. Closing the Locks. If the locks at the CRCW and O’Brien

are closed, the states concede that the closure need not be

permanent or unqualified; instead, they say, the locks may

be opened if closure would put public health or safety at

risk. We are not sure how that would work. The City of

Chicago says that police and fire services use the locks

routinely, as do Coast Guard boats. At one point, the states
No. 10-3891 43

agreed that passage for emergency boats through the locks

was needed for public safety. That sounds reasonable to us.

Now, however, theirinjunction would allow the defendants

to open the locks only when the District needs to release

water from the CAWS into the lake to control flooding

(during so-called “reversal” operations). The states’

proposed injunction is made more effective by keeping the

locks closed to all boat traffic, but in so doing, it increases

the cost to emergency services. Even in its current iteration,

the efficacy of the states’ plan for closing the locks is

compromised because any flooding that would require the

defendants to conduct reversal operations decreases the

chances that the carp will be stopped – when the locks are

open, water pours out of the CAWS and into Lake Michigan.

(This happened most recently on July 24, 2011, after nearly

seven inches of rain fell in only two hours, see Michelle

Gallardo, 2 Locks Opened During Record Rainfall, Chicago

Tribune, July 25, 2011, http://abclocal.go.com/wls/story?

section=news/ local&id=8270514. It also happened exactly

one year before, on July 24, 2010.) A related complication

concerns how effectively the locks stop fish even when they

are closed. By most accounts, a watertight closure would

require bulkheads to be installed on the locks. Without

bulkheads, fish might slip through small openings. The

states have been less than explicit about whether their ideal

injunction would require bulkheads, but if it would, then all

the risks of flooding come right back into the equation.

Bulkheads take time to install and remove, which means

that it would be very difficult to respond quickly to floods.

In short, this aspect of the states’ requested relief puts them

into a bind: the risk of carp migration is reduced the most by

closing the locks permanently with bulkheads; but that

measure, as the states recognize, would dramatically

escalate the costs imposed by flooding. While keeping the

locks closed more often no doubt reduces the risk of fish

migrating into Lake Michigan, it does not bring it down to

zero. And this unquantified reduction in risk comes with an

increased immediate burden on public health and safety

measures.
44 No. 10-3891

b. Screens over Sluice Gates. The states encounter similar

problems with their request that the defendants screen off

nine additional sluice gates. The District operates these huge

gates, which open and close to adjust the rate of water flow,

as part of its diversion effort – the process of drawing water

out of Lake Michigan and into the CAWS to maintain

navigability and water quality. In addition, when heavy

rains occur, sluice gates (like the locks) are opened to let

water from the CAWS into the lake. There are eight sluice

gates at the Controlling Works, four at O’Brien, and one in

Wilmette. To prevent the migration of adult carp, the

District already has installed four screens over sluice gates:

two at the Controlling Works and two at O’Brien. The

District uses the four screened-off gates for diversion; the

other nine remain closed except during flooding.

Initially, the states wanted to force the defendants to close

all of the gates, except when public health or safety might be

harmed. They have revised thatrequest so that now they ask

for screens over the nine remaining sluice gates at these

sites. This request would mitigate the risk of carp migration

only (at best) during floods, for at other times the gates,

unlike the locks, are closed anyway. Further reducing the

effectiveness of this measure is the fact that in some flooding

incidents where additional sluice gates must be opened, the

locks must be opened as well. Screens over additional sluice

gates would not do much good if fish could swim through

open locks. Finally, all available evidence suggests that it

will take a long time for the District to acquire additional

property, to research feasible options for a system of screens

that will not become clogged with debris during flooding,

and to build those screens. This means that this portion of

the states’ preliminary injunction might not even be in place

before the full trial on the merits has concluded. For all of

these reasons, we think that installing screens over sluice

gates will have at most a tiny effect on the odds of invasive

carp making it to Lake Michigan.

c. Block Nets in the Rivers. The prospect of placing block

nets in the Little Calumet and Grand Calumet Rivers strikes
No. 10-3891 45

us as potentially the most effective element of the proposed

relief. At the time of oral argument, the states asked that the

Corps place block nets only in the Little Calumet River; at

that point, a cofferdam in the Grand Calumet River

prevented fish migration and alleviated the need for nets

there. We will assume that were this dam removed, the

states would ask the Corps to place nets in the Grand

Calumet River as well. The Corps, however, has said that it

is already looking at the possibility of installing nets in both

waterways, but that it is concerned that flooding will

increase as debris becomes caught in the nets. The states

respond that block nets could be cut free and replaced with

new nets if risks of flooding materialized. All of the parties

are vague about the possibilities and implications of this

plan. At this stage, it is enough to say that this step seems

more promising than others when it comes to mitigating the

risk that fish will appear in Lake Michigan. We take the

Corps at its word that this option is under serious

consideration and would be implemented if and when a

feasible plan can be developed.

d. Rotenone Poisoning. In contrast to the block net idea, the

suggestion that the Corps use rotenone to poison fish in the

CAWS seems untenable to us. Rotenone is a chemical that

acts as a piscicide when it is released in a body of water.

Though humans would not digest much of it if it were

ingested, rotenone enters the bloodstream of a fish through

the gills, causing death quickly. Rotenone dumped into a

river kills the vast majority of fish living there; when dead,

they usually float to the surface. The poison generally is less

dangerous to other animals, but it is toxic and its toxicity

varies depending on the species. See generally Cornell

University, Resource Guide for Organic Insect and Disease

Management, Material Fact Sheets - Rotenone,

http://web.pppmb.cals .cornell.edu/resourceguide/

mfs/11rotenone.php. It is unclear just how the states’

proposal for rotenone use differs from what the Corps is

already doing in the CAWS. We know that the states would

like poison to be applied near O’Brien, but there is no
46 No. 10-3891

indication how often or where else it might be used. In May

2010, the Corps and other agencies used the poison to search

for fish in a two-mile stretch of the Little Calumet River.

Dozens of tons of fish were killed, and no specimens of

invasive carp were found. While poisoning may be an

effective way to search for elusive carp in some

circumstances, the record does not explain why ordering the

Corps to poison the CAWS on a regular basis would be a

sound step toward reducing the risk that invasive carp will

migrate into the Great Lakes.

e. Accelerating GLMRIS. That brings us to the aspect of the

proposed injunction that would require the Corps to

accelerate its long-term study of ways in which it might

permanently prevent the migration of invasive species

(including, but not limited to, the carp) between the Great

Lakes and the Mississippi basins. The states raise a side

issue here, saying that the district court erred when it denied

their request to expedite GLMRIS because it failed to make

the findings required by Federal Rule of Civil Procedure

52(a)(2). The argument is frivolous. The district court

explained its reasons for denying all of the relief that the

states sought. The court had – and will continue to have as

the case moves forward – the power to grant or deny

equitable measures eitherin whole or in part. It did not need

to discuss every facet of the relief requested.

According to the Corps, GLMRIS examines every potential

pathway between the two watersheds and proposes

solutions to stop migration through each one. Examination

of the CAWS, which the Corps intends to finish by 2015, is

just one portion of the study. The Corps adds that it has the

power to implement solutions that are devised as the study

progresses. The states would like the court to order the

Corps to finish the CAWS portion of GLMRIS within 18

months. They are not the only ones who have criticized the

study for taking too long; the City of Chicago and others

have as well. See, e.g., Dan Egan, Chicago Urges Army Corps

to Report on Carp Sooner, Milwaukee Journal Sentinel, Apr.

1 0 , 2 0 1 1 , h t t p : / / w w w . j s o n l i n e . c o m /
No. 10-3891 47

news/wisconsin/119547049.html. It may well be that faster

action is appropriate if possible; and, as the Corps conceded

during oral argument, it may be necessary for the Corps to

implement measures devised through GLMRIS on a rolling

basis. But we do not see how a preliminary injunction that

would essentially ask the Corps to study harder and think

faster would reduce the odds that invasive carp will

establish themselves in the short term.

When we take all five aspects of the states’ proposed

injunction together, we can say only that there is some

evidence that the relief sought would reduce by an

undefined amount the risk of carp establishing a breeding

population in the Great Lakes. It is equally apparent,

however, that the steps the states have proposed offer no

assurance that they will block the carp over the short run or,

over the long run, that they will save the Great Lakes

ecosystem and the $7 billion industry that depends on that

ecosystem. We must therefore turn to the other side of the

equation: the harm that the proposed steps would inflict on

the opponents of preliminary relief.

3

The states have adopted a ratherinsouciant attitude about

the potential harm that their proposal might inflict. “[T]he

federal government has made it clear that it is willing to

spend significant resources to reduce this threat,” the states

write, “so the cost of a few bulkheads should not prove a

serious impediment to protecting the Great Lakes.” This

tone continues throughout their briefs, with remarks like,

“While the Corps asserts that the Coast Guard doesn’t have

the funds to [dock additional ships on both sides of locks

that would be closed by the injunction], this is just a matter

of money.” Of course this dispute is in part a matter of

money; but scoffing at the defendants’ concerns about the

costs of relief does not aid our assessment of the expense of

the relief that the states want. It should go without saying in

these straitened times that the federal and local governments

do not have bottomless coffers. Indeed, 19 members of the
48 No. 10-3891

plaintiff states’ delegations to Congress recently voted

against raising the federal borrowing limit. Nor do we

understand why the states take this view when they

apparently feel no obligation to contribute to the costs of

averting this crisis. When we inquired at oral argument how

the costs of the proposed injunction should be apportioned

among the parties, the states informed us that their citizens

would contribute to the costs by paying federal income

taxes. This is not very helpful. Indeed, one might wonder

why the federal government and the State of Illinois should

be saddled with the entire cost of an injunction that is aimed

at a problem that has been developing for four decades in a

watershed that touches roughly half of the states in the

Union.

To make matters worse, both sides throw around large

numbers to make the case that the balance of harms favors

their position.We have already explained why the proposed

injunction is quite unlikely to prevent the states’ forecasted

$7 billion in harm. But the defendants invent similarly

extreme costs. We are told repeatedly that almost $2 billion

in cargo moves through locks in the CAWS each year. This,

however, is not the cost that an injunction would impose on

commercial shipping. If the locks were closed, cargo would

have to be loaded from ships onto ground transportation at

some point along the journey. Estimates of the cost of

off-loading range from about $70 million per year (from the

plaintiffs’ perspective) to $150 million (according to the

Corps). The intervening defendant Coalition to Save Our

Waterways, which represents various business interests,

tells us that closing the locks would cost $4.7 billion. We find

no support in the record for that astronomical estimate. The

dollar value of the harm to either side is of course difficult to

calculate, but we need not settle on a precise number to

resolve this appeal.

If the requested preliminary injunction were to issue, we

can be sure that it would impose significant costs. First, we

would have the expenses of implementing all of the

measures that the states have recommended. In addition,
No. 10-3891 49

funds that the defendants spend complying with the

injunction likely would be diverted from other agency

efforts to curb invasive carp. If we required the Corps to

complete its long-term study within 18 months, the Corps

suggests that it would not have time study the problem

comprehensively and that the study might not adequately

support any proposed solutions. The prospect of closing the

locks permanently, installing screens on sluice gates, and

placing block nets in the CAWS increases the risk of

flooding, which (to the extent that it occurs) would impose

costs throughout the region. The states say that there are

ways to avoid those costs. The locks, for example, could be

opened at the District’s discretion during flooding. But, as

we have explained, this would be possible only if the states

agreed that bulkheads were not necessary. (The states argue

that bulkheads could be removed by a barge and crane to

permit for flood relief. Even if that were possible, stationing

barges at both locks would cost thousands of dollars per

day.) Screens installed over sluice gates used during

flooding could become clogged, and the states’ suggestion

that raking systems be installed to alleviate this concern is

both untested and would required significant additional

expenditures. Meanwhile, closing the locks to boat traffic

would have a tremendous impact. Police and fire services on

which the City of Chicago relies would not be able to move

from the Chicago River and other points in the CAWS to

Lake Michigan, which means that the city would have to

establish redundant emergency response fleets on either side

of the locks. The same goes for Coast Guard operations

around the CAWS. Recreational and tourist vessels would

be stopped. And last but certainly not least, closed locks

would mean that all commercial shipping in the area

between the Great Lakes and the Mississippi would have to

find alternative routes.

We can stop there. This overview demonstrates that the

preliminary injunction the states have requested would

impose substantial costs, yet given the current state of the

record, we are not convinced that the preliminary injunction
50 No. 10-3891

would assure much of a reduction in the risk of the invasive

carp establishing themselves in Lake Michigan in the near

future. That the balance of harms at this stage of the

litigation favors the defendants might be enough by itself to

support a conclusion that preliminary relief is not

warranted, even though we have concluded that the states

have demonstrated a likelihood of success on the merits and

a threat of irreparable harm. See Hoosier Energy Rural Elec.

Co-op v. John Hancock Life Ins. Co., 582 F.3d 721, 725 (7th Cir.

2009) (describing the relation between the harm prevented

by the plaintiff’s proposed injunction and the strength of a

plaintiff’s claim for preliminary relief). Even if one were to

conclude that the harms are in equipoise, however, there is

a final reason why preliminary injunctive relief is not

warranted. As things now stand, the case for judicial

intervention is refuted by the fact that the competent federal

and state actors are actively pursuing an array of efforts to

solve the problem of invasive carp.

B

1

While American Electric Poweris a case about congressional

displacement of federal common law, the Supreme Court

took the opportunity to touch generally on the relative

competence of courts and expert agencies when it comes to

solving complex environmental problems. “It is altogether

fitting that Congress designated an expert agency, here,

EPA, as best suited to serve as primary regulator of

greenhouse gas emissions,” the Court wrote, explaining

further:

The expert agency is surely better equipped to do the job

than individual district judges issuing ad hoc,

case-by-case injunctions. Federal judges lack the

scientific, economic, and technological resources an

agency can utilize in coping with issues of this order.

Judges may not commission scientific studies or

convene groups of experts for advice, or issue rules

under notice-and-comment procedures inviting input by
No. 10-3891 51

any interested person, or seek the counsel of regulators

in the States where the defendants are located. Rather,

judges are confined by a record comprising the evidence

the parties present. Moreover, federal district judges,

sitting as sole adjudicators, lack authority to render

precedential decisions binding other judges, even

members of the same court.

American Electric Power, 131 S. Ct. 2539-40 (internal citation

omitted). This limitation of the judiciary is a familiar feature

of American law. See, e.g., Negusie v. Holder, 129 S. Ct. 1159,

1171 (2009) (Stevens, J., concurring in part and dissenting in

part); Kelo v. City of New London, 545 U.S. 469, 487-88 (2005);

Lingle v. Chevron U.S.A., Inc., 544 U.S. 528, 544-45 (2005);

Chevron, U.S.A., Inc. v. Natural Res. Def. Council, Inc., 467 U.S.

837, 865-66 (1984); Tennessee Valley Authority v. Hill, 437 U.S.

153, 194-95 (1978).

Our sister circuits have explored the impact of this

inherent limitation of the judicialrole in cases comparable to

ours. The Second Circuit has written that “[c]ourts

traditionally have been reluctant to enjoin as a public

nuisance activities which have been considered and

specifically authorized by the government.” New England

Legal Found. v. Costle, 666 F.2d 30, 33 (2d Cir. 1981). In the

same vein, the Fourth Circuit recently reversed a lower

court’s decision to enter an injunction that would have

required the TVA to implement new emissions controls.

North Carolina, ex rel. Cooper, 615 F.3d 291. The district court

in that case entered an injunction after North Carolina sued

the TVA for air pollution based on a state common-law

public nuisance theory. The court of appeals concluded that

granting “the injunction would encourage courts to use

vague public nuisance standards to scuttle the nation’s

carefully created system for accommodating the need for

energy production and the need for clear air.” Id. at 296.

Though the case involved a more robust regulatory scheme

than the one that has been cobbled together for the invasive

carp, the court’s discussion is instructive insofar as it relates

to the problems created when courts attempt to stop a
52 No. 10-3891

nuisance at the same time that agencies are working to solve

the problem. An approach that would allow the federal

court and the EPA simultaneously to regulate a single

emissions problem, said the Fourth Circuit, would result in

multiple and perhaps contradictory decrees emanating from

different branches of government and confusion about what

standards should govern air pollution. Id. at 301-04. In

addition, judicial action in the face of strong agency

measures “would reorder the respective functions of courts

and agencies.” Id. at 304. Environmental problems require

the balancing of many complicated interests, and agencies

are better suited to weigh competing proposals and select

among solutions. Id. at 305 (“[W]e doubt seriously that . . . a

judge holding a twelve-day bench trial could evaluate more

than a mere fraction of the information that regulatory

bodies can consider.”).

None of this means that courts can no longer craft

remedies designed to abate a public nuisance. In light of the

general approach the Supreme Court took in American

Electric Power, however, it does mean that the court should

not blind itself to otherremedies that are available underthe

law or to other measures that are actively being pursued to

solve the problem. Even if legal displacement like that found

in American Electric Power does not exist, the practical effect

of agency actions might add up to displace as a matter of

fact any role that equity might otherwise play. Efforts of

other branches of government might be so complete that

additional action ordered by a court would risk

undermining agency efforts to abate the nuisance. How

much the equitable power of the court has been limited by

agency action will be a factual question that turns on the

quality and quantity of the agency’s (or, as here, agencies’)

efforts. This kind of institutional consideration of the court’s

relative ability to craft meaningful relief fits naturally in the

balance-of-harms analysis. For if an injunction might

hamper agency efforts or can improve upon them only

slightly, that is all the more reason to conclude that the

equities tilt in favor of the defendant.
No. 10-3891 53

2

The record in this case leaves no doubt that federal and

state agencies, executive officials, and working groups have

mounted a tremendous effort to halt the migration of

invasive carp. As we have already mentioned, the Aquatic

Nuisance Prevention and Control Act of 1990 created the

Aquatic Nuisance Species Task Force, which includes among

other agencies the National Oceanic and Atmospheric

Administration, the U.S. Fish and Wildlife Service, the U.S.

Geological Survey, and the EPA. This task force coordinates

invasive species issues generally across the country. In

addition, during the fall of 2009, 21 federal, state, and local

agencies and other entities combined forces to form the

Asian Carp Regional Coordinating Committee (the ACRCC),

which is designed (as the name suggests) to track and to

stop the migration of invasive carp. See generally Asian

Carp Control, http://www.asiancarp.org/. The ACRCC

counts as members those agencies that comprise the task

force, the Corps and the District, the Coast Guard, the U.S.

Department of Transportation, the White House Council on

Environmental Quality, the Great Lakes Fishery

Commission, the City of Chicago, and the state departments

of natural resources of all of the plaintiff states, plus Illinois,

Indiana, and New York.

In order to stop the invasive carp, the ACRCC has

developed what it calls the “Asian Carp Control Strategy

Framework,” which is now in its third edition. The most

recent document lists over 40 collaborative projects that the

working group has designed to deal with invasive carp;

many of these initiatives are underway or have been

completed already. As the ACRCC describes it, the projects

fall into eight categories:

(1) targeted monitoring assessment activities above and

below the electric barrier system, including enhanced

monitoring above and below the barriers, electrofishing,

and rapid response teams;

(2) commercial harvesting and removal actions below
54 No. 10-3891

the electric barriers (which involves fishing and removal

of fish in the Lockport area, where the CAWS connects

to the Des Plaines River; creating new markets for the

fish; and investigating certification requirements for

invasive carp to be sold commercially);

(3) electric barrier actions and waterway separation

measures (consisting of the construction of barriers

between various waterways so that fish cannot move

from one to the other during flooding; expedited

construction of the now-completed third electric barrier;

fish tagging to test the effectiveness of the barriers; and

separation of various watersheds that pose risks);

(4) myriad studies on how best to separate the

watersheds; the effectiveness of various measures; and

risk modeling;

(5) research and technology development (including

investigation of how fish move around the CAWS; food

sources for invasive carp in the lakes and how those

sources might be eliminated; the use of seismic

technology to divert or kill invasive carp; attraction and

repulsion pheromones of invasive carp; creation oftoxin

screens to kill fish; study of the weaknesses of carp to

different toxins; physical barriers; reducing carp egg

viability; and new detection methods, among other

things);

(6) eDNA analysis and refinement (which involves

monitoring and sampling for eDNA in the CAWS and

increasing the effectiveness of eDNA testing);

(7) enforcement activities designed to prevent people

from transferring carp between bodies of water; and

(8) work on funding, including the development of

methods to pay for measures among the contributing

groups.

In addition, the ACRCC has established three working

groups: monitoring and rapid response; invasion control;
No. 10-3891 55

and communication and outreach.

What we have described already reflects a substantial

effort, but there is more. The Corps has been fulfilling the

marching orders that it has received from Congress. In

addition to the electric barriers and GLMRIS, which we have

discussed in detail, we have mentioned the Corps’s study of

the effectiveness of its three electric barriers for stopping the

movement of invasive carp through the CAWS. The final

version of the Efficacy Study is due later this year, but there

already have been fourinterim reports (numbered in typical

bureaucratic fashion as Interim I, II, III, and IIIA), and the

Corps has implemented measures pursuant to some of these

reports. Interim I identified an area where the Des Plaines

River and the Chicago Sanitary and Ship Canal are so close

together that carp could wash between them during floods.

(The plaintiffs had argued in their complaint that this area

represented a huge problem.) The Corps has since built a

fence to stop migration between these waterways, and that

fence has already proven effective. Meanwhile, Interim II,

which is not yet completed, will set operational parameters

forthe three electric barriers so that they can most effectively

deter the movement of invasive species. The Corps says that

even though this study is not finished, it now operates the

barriers at the maximum safe strength.In connection with its

Interim III report, the Corps consulted a panel of experts

about a number of potential changes to its operation of the

CAWS. The report concluded that additional screens should

be installed on sluice gates, and the District responded by

adding screens to two gates at O’Brien, which supplemented

the two it had installed months earlier at the Controlling

Works. In addition, Interim III recommended that the

District cease using the sluice gate at Wilmette for diversion,

and it hypothesized that the District might be able to create

“atoxic zones” in the CAWS that would be so toxic that no

fish would ever be able to swim through them. Finally, the

Corps in Interim IIIA recommended the construction of an

acoustic, air-bubble, and strobe-light curtain (more or less a

disco screen), which would be designed to frighten fish back
56 No. 10-3891

toward the Mississippi. The disco screen has not been

started, but the Corps represented to us at oral argument

that it intends to undertake the project at some location

downstream of the existing electric barriers.

In addition to the measures outlined in the interim efficacy

reports, the agencies continue to rely on traditional methods

to monitor and kill invasive carp, including tracking,

netting, electrofishing, and rotenone poisoning; and, as we

have discussed, they have also continued eDNA testing

throughout the CAWS. Where eDNA reveals a potential

threat, the agencies have responded with days-long hunts

for invasive carp. Continual fishing south of the CAWS

reduces the propagule pressure that would otherwise push

carp closer to Lake Michigan. Finally, the Obama

Administration has named an “Asian carp czar,” who is

charged with leading the administration’s effort to stop

invasive carp.Recently, the administration announced plans

to install a high-intensity water cannon that would deterfish

by firing huge, underwater blasts of water across Chicago

Ship and Sanity Canal.

It is our understanding that the defendants and the

agencies we have just discussed are actively pursuing the

measures that we have just described. In addition, where the

defendants have represented that future steps will be taken

– whether a disco screen, the water gun, operating the

electric barriers at optimal settings, considering the

possibility of block nets in the CAWS, completing and

implementing GLMRIS in phases, continuing to monitor

aggressively with traditional and eDNA techniques, or any

of the other actions we have highlighted – we have no

reason at this point to assume that this work will not be

done. Whatever happens, the plaintiff states will continue to

have a seat at the table as these and future plans are made

and implemented. We conclude that on this record, there is

nothing that any preliminary injunction from the court could

add that would protect the Great Lakes from invasive carp

while this suit is being adjudicated any better than the

elaborate measures we have just described. This tips the
No. 10-3891 57

balance of harms decisively in favor of the defendants.

VI

We take very seriously the threat posed by the invasive

species of carp that have come to dominate parts of the

Mississippi River basin and now stand at the border of one

of the most precious freshwater ecosystems in the world.

Any threat to the irreplaceable natural resources on which

we all depend demands the most diligent attention of

government. As the case proceeds, the district judge should

bear in mind that the risk of harm here depends upon both

the probability of the harm and the magnitude of the

problem that would result.In the end, however, the question

whether the federal courts can offer meaningful equitable

relief – either preliminary or permanent – to help abate a

public nuisance in the face of agency action is factual in

nature . It depends on the actual measures that the agencies

have implemented already and those that they have

committed to put in place going forward. Our ruling today

is tied to our understanding of the current state of play. We

recognize that the facts on the ground (orin the water) could

change. The agencies currently working hard to solve the

carp problem might find themselves unable to continue, for

budgetary reasons, because of policy changes in

Washington, D.C., or for some other reason. If that happens,

it is possible that the balance of equities would shift.

Similarly, new evidence might come to light which would

require more drastic action, up to and including closing

locks on Lake Michigan for a period of time. If either

situation comes to pass, then the district court would have

the authority to revisit the question whether an exercise of

its equitable powers is warranted, taking into account the

principles we have discussed in this opinion. As things

stand now, however, preliminary relief is not appropriate.

The district court’s judgment is AFFIRMED.