Amicus Curiae Brief — Suncor Energy (U.S.A.) Inc., et al., Petitioners v. County Commissioners of Boulder County, et al.

No. 25-170

In the

Supreme Court of the United States

SUNCOR ENERGY (U.S.A.) INC., et al.,

Petitioners,

v.

COUNTY COMMISSIONERS OF

BOULDER COUNTY, et al.,

Respondents.

On Writ of Certiorari to the

Supreme Court of Colorado

BRIEF OF THE CENTER FOR ENVIRONMENTAL

ACCOUNTABILITY AS AMICUS CURIAE

IN SUPPORT OF PETITIONERS

Paul E. Salamanca

Counsel of Record

279 Cassidy Avenue

Lexington, KY 40502

(859) 338-7287

psalaman20@gmail.com

Counsel for Amicus Curiae

121021

A

(800) 274-3321 • (800) 359-6859

i

TABLE OF CONTENTS

Page

TABLE OF CONTENTS . . . . . . . . . . . . . . . . . . . . . . . . . . i

TABLE OF CITED AUTHORITIES . . . . . . . . . . . . . . . ii

INTEREST OF AMICUS CURIAE . . . . . . . . . . . . . . . . 1

SUMMARY OF THE ARGUMENT . . . . . . . . . . . . . . . 1

ARGUMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

I.

This Court has Jurisdiction to Hear This Case . . 3

II. Federal Common Law Precludes Respondents’

Claims . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

III. Rescission of the Endangerment Finding

Does Not Alter the Outcome of This Case . . . . 14

IV. No Court and No Jury Could Feasibly

Address Respondents’ Allegations . . . . . . . . . . 16

CONCLUSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

ii

TABLE OF CITED AUTHORITIES

Page

Cases

American Electric Power Co., Inc. v. Connecticut,

564 U.S. 410 (2011) . . . . . . . . . . . . . . . . . . . . . . . 2, 6, 15

Atlantic Richfield Co. v. Christian,

590 U.S. 1 (2020) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4

Bandini Petroleum Co. v. Superior Court,

284 U.S. 8 (1931) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Bendix Autolite Corp. v. Midwesco Enterprises, Inc.,

486 U.S. 888 (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Boomer v. Atlantic Cement Co., Inc.,

26 N.Y.2d 219 (1970) . . . . . . . . . . . . . . . . . . . . . . . . . . 16

City of Denver v. Mullen,

3 P. 693 (Colo. 1884) . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

City of New York v. Chevron Corp.,

993 F.3d 81 (2021) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Clearfield Trust Co. v. United States,

318 U.S. 363 (1943) . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Cox Broadcasting Corp. v. Cohn,

420 U.S. 469 (1975) . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 6

Erie Railroad Co. v. Tompkins,

304 U.S. 64 (1938) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

iii

Cited Authorities

Page

Fisher v. District Court,

424 U.S. 382 (1976) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Hinderlider v. La Plata River &

Cherry Creek Ditch Co.,

304 U.S. 92 (1938) . . . . . . . . . . . . . . . . . . . . . . . . 6-10, 15

Hoery v. United States,

64 P.3d 214 (Colo. 2003) . . . . . . . . . . . . . . . . . . . . . . . 16

Illinois v. City of Milwaukee,

406 U.S. 91 (1972) . . . . . . . . . . . . . . . . . . . . . 2, 9, 10, 15

International Paper Co. v. Ouellette,

479 U.S. 481 (1987) . . . . . . . . . . . . . . . . . . . . . . . . 14, 15

Jesner v. Arab Bank, PLC,

584 U.S. 241 (2018) . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Kansas v. Colorado,

206 U.S. 46 (1907) . . . . . . . . . . . . . . . . . . . . . . 2, 8-10, 15

Kurns v. R.R. Friction Prods. Corp.,

565 U.S. 625 (2012) . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

M.D.C./Wood, Inc. v. Mortimer,

866 P.2d 1380 (Colo. 1994) . . . . . . . . . . . . . . . . . . . . . 12

Madruga v. Superior Court,

346 U.S. 556 (1954) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

iv

Cited Authorities

Page

Massachusetts v.

Environmental Protection Agency,

549 U.S. 497 (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Missouri v. Illinois,

200 U.S. 496 (1906) . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

National Pork Producers Council v. Ross,

598 U.S. 356 (2023) . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Northeast Bancorp, Inc. v. Board of Governors

of the Fed. Reserve Sys.,

472 U.S. 159 (1985) . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Public Serv. Co. v. Van Wyck,

27 P.3d 377 (Colo. 2001) . . . . . . . . . . . . . . . . . . . . . . . . 16

Rescue Army v. Municipal Court,

331 U.S. 549 (1947) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

San Diego Bldg. Trades Council v. Garmon,

359 U.S. 236 (1959) . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Texas Industries, Inc. v. Radcliff Minerals, Inc.,

451 U.S. 630 (1981) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

United States v. Kimbell Foods, Inc.,

440 U.S. 715 (1979) . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

United States v. Locke,

529 U.S. 89 (2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

v

Cited Authorities

Page

Vincent v. Lake Erie Transp. Co.,

124 N.W. 221 (Minn. 1910) . . . . . . . . . . . . . . . . . . . . . 16

World-Wide Volkswagen Corp. v. Woodson,

444 U.S. 286 (1980) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Constitutional Provisions

U.S. Const. art. VI, cl. 2 . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Statutes and Other Authorities

28 U.S.C. § 1257 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4, 5

28 U.S.C. § 1257(3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

28 U.S.C. § 1257(a) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5

42 U.S.C. § 7401 et seq. . . . . . . . . . . . . . . . . . . . . . . . 2, 3, 15

Alien Tort Statute . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Am. Pub. Health Ass’n v. U.S. Envtl. Prot. Agency,

D.C. Cir., No. 26-1037 (petition filed Feb. 18, 2026) . 3, 15

Amicus curiae brief in support of petitioners,

Seven County Infrastructure Coalition v.

Eagle County, 605 U.S. 168 (2025), https://

environmentalaccountability.org/publications/

(last visited May 18, 2026) . . . . . . . . . . . . . . . . . . . . . . 1

vi

Cited Authorities

Page

Peter H. Aranson, The Common Law as Central

Economic Planning, 3 Const. Pol. Econ. 289 (1992) . . 17

James M. Buchanan, Positive Economics, Welfare

Economics, and Political Economy, 2 J. L. & Econ.

124 (1959) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17, 18

Stephen Castle, Why London’s Chimney Sweeps

Are Enjoying a Resurgence, N.Y. Times, Jan. 18,

2026 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Andrew J. Cherlin, Labor’s Love Lost: The Rise and

Fall of the Working-Class Family in America 174

(2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Colorado Appellate Rule 21 . . . . . . . . . . . . . . . . . . . . . . . . 3

Tom Fairless, European Businesses Weathered

War Storm, Wall St. J., Mar. 25, 2023 . . . . . . . . . . . 18

Henry J. Friendly, In Praise of Erie—And of the

New Federal Common Law, 39 N.Y.U. L. Rev.

383 (1964) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

International Energy Agency, A Vision for Clean

Cooking Access for All (2023) . . . . . . . . . . . . . . . . . . 19

Judicial Code § 237(a) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

vii

Cited Authorities

Page

Rescission of the Greenhouse Gas Endangerment

Finding and Motor Vehicle Greenhouse Gas

Emission Standards Under the Clean Air Act,

91 Fed. Reg. 7686 (Feb. 18, 2026) . . . . . . . . . . . . . 3, 14

Restatement (2d) of Torts § 826, cmt. d . . . . . . . . . . . . 16

Tibor Scitovsky, Two Concepts of External

16Economies, 62 J. Pol. Econ. 143 (1954) . . . . . . . . . 19

William Julius Wilson, When Work Disappears:

The World of the New Urban Poor 73 (1996) . . . . . . 18

1

INTEREST OF AMICUS CURIAE

The Center for Environmental Accountability

(CEA) is a non-profit organization whose mission is to

promote transparency, excellence, and accountability

in environmental policy, as well as fidelity to the rule of

law.1 Its commitment to a healthy environment includes

commitment to a healthy human environment, such

that people from all walks of life can thrive. To date, it

has submitted at least sixteen distinct sets of comments

to agencies at the federal and state level in at least

twelve different areas of environmental law and policy,

including many issues touching on energy and climate.

It also submitted an amicus curiae brief in support of

petitioners in Seven County Infrastructure Coalition v.

Eagle County, 605 U.S. 168 (2025). 2 CEA respectfully

submits that its broad familiarity with environmental law

and policy, together with its specific insights on energy and

climate, enable it to be of considerable help to the Court.

SUMMARY OF THE ARGUMENT

Jurisdiction here is clear. The judgment below finally

resolved a self-contained original action. Under settled

precedent, that is sufficient. See Atlantic Richfield Co. v.

1. No counsel for a party wrote this brief in whole or in part,

and no party or counsel for a party made a monetary contribution

intended to pay for the preparation or submission of this brief. No

person or entity other than amicus curiae or its counsel made a

monetary contribution to the preparation or submission of this

brief.

2. See https://environmentalaccountability.org/publications/

(last visited May 18, 2026).

2

Christian, 590 U.S. 1, 12 (2020). This case also satisfies the

criteria for the fourth category of Cox Broadcasting Corp.

v. Cohn. See 420 U.S. 469, 482-83 (1975). The Supreme

Court of Colorado rejected petitioners’ claim of federal

preemption; reversal by this Court on that issue would

end the case; and vital federal interests are at stake.

On the merits, federal law squarely precludes

respondents’ actions. For over a century, this Court has

recognized that federal common law controls disputes over

“air and water in their ambient or interstate aspects.”

Illinois v. City of Milwaukee, 406 U.S. 91, 103 (1972)

(Milwaukee I). See also Kansas v. Colorado, 206 U.S. 46,

98 (1907) (resolving an interstate water dispute according

to “what may not improperly be called interstate common

law”). This is because the structure of our Constitution

requires a federal rule of decision where sovereigns of

equal dignity lay claim to the same resource. This is

exactly such a case. Several municipalities in Colorado

are facing off against every other state—and the rest

of the world, for that matter—over access to the global

upper atmosphere.

To be sure, this case also implicates the Clean Air

Act, 42 U.S.C. § 7401 et seq., which itself may preempt

respondents’ claims. But that does not change the outcome

of this case. If the Clean Air Act does not “speak directly”

to greenhouse gases, then federal common law controls,

precisely as it did in Milwaukee I and Kansas v. Colorado.

American Electric Power Co., Inc. v. Connecticut, 564

U.S. 410, 424 (2011) (cleaned up). And if, by contrast, the

Act does speak directly to greenhouse gases, then the

interaction of federal common law and the Act would

equally preempt respondents’ claims, because nothing

3

in the Act displaces the structural truth that sovereigns

of equal dignity cannot impose their laws on each other.

Nor would rescission of the Endangerment Finding

affect this analysis. See Rescission of the Greenhouse Gas

Endangerment Finding and Motor Vehicle Greenhouse

Gas Emission Standards Under the Clean Air Act, 91 Fed.

Reg. 7686 (Feb. 18, 2026). Whether or not the rescission

stands up to challenge, see, e.g., Am. Pub. Health Ass’n v.

U.S. Envtl. Prot. Agency, D.C. Cir., No. 26-1037 (petition

filed Feb. 18, 2026), and whatever the rescission’s effect

on the EPA’s authority under the Clean Air Act, the Act

either does or does not “speak directly” to respondents’

claims, and under either possibility respondents’ claims

are precluded.

ARGUMENT

I.

This Court has Jurisdiction to Hear This Case.

Jurisdiction here is clear. The case below was an

original action under Colorado Appellate Rule 21, and

the decision by the Supreme Court of Colorado to deny

relief was a final judgment disposing of that action. 28

U.S.C. § 1257(a) empowers this Court to review such

judgments if a party asserts a right or immunity based on

the Constitution or laws of the United States. Petitioners

did exactly that, arguing that respondents’ claims against

them were precluded by the Constitution itself or by the

Clean Air Act.

Respondents’ arguments to the contrary are not

persuasive. Far from being anomalous, Atlantic Richfield

Co. v. Christian follows a long line of cases. 590 U.S. 1

4

(2020). In Fisher v. District Court, 424 U.S. 382 (1976),

for example, a Montana trial court dismissed an adoption

proceeding on the ground that exclusive jurisdiction lay

with a Cheyenne tribal court. The would-be parents asked

the Supreme Court of Montana for a “writ of supervisory

control or other appropriate writ to set aside the order

of dismissal.” Id. at 385. The Court granted the writ,

concluding that the lower court in fact had jurisdiction

to hear the case. The child’s mother, Fisher, then sought

review in this Court, which reversed on the merits. The

Court saw no impediment to hearing the case, writing as

follows in a footnote:

The writ of supervisory control issued by

the Montana Supreme Court is a final judgment

within our jurisdiction under 28 U.S.C. § 1257(3)

[a predecessor of § 1257(a)]. It is available only in

original proceedings in the Montana Supreme

Court, and although it may issue in a broad

range of circumstances, it is not equivalent to

an appeal.

Id. at 385 n.7 (some citations omitted) (emphasis added).

The famous case of World-Wide Volkswagen Corp.

v. Woodson similarly arose from denial of a writ of

prohibition by the Supreme Court of Oklahoma. 444 U.S.

286 (1980). In this case, World-Wide appeared specially

in state court to contest personal jurisdiction. After the

court overruled its objections, it unsuccessfully sought a

writ of prohibition from the Supreme Court of Oklahoma.

It then took its case to this Court, which reversed, per

Justice White, without even addressing the question of

whether the decision by the Supreme Court of Oklahoma

was final for purposes of § 1257.

5

Another example is Bandini Petroleum Co. v.

Superior Court, 284 U.S. 8 (1931). Bandini began as an

action by the state in state court to enjoin waste of natural

gas. The court granted a preliminary injunction against

Bandini, which then asked an intermediate appellate

court for a writ of prohibition. Bandini argued that the

trial court lacked jurisdiction to hear the case because the

statute on which the state was suing denied due process.

The intermediate appellate court denied relief, and the

Supreme Court of California refused to hear Bandini’s

appeal. This Court accepted the case. “This Court has

jurisdiction,” wrote Chief Justice Hughes for the Court.

“The proceeding for a writ of prohibition,” he continued,

“is a distinct suit and the judgment finally disposing of it

is a final judgment within the meaning of § 237(a) of the

Judicial Code [a predecessor of § 1257(a)].” Id. at 14. 3

Respondents may argue that what matters is not the

form of the action below, but its substance, that is, whether

the decision below actually terminated the litigation in

state court. See Brief in Opposition [to Petition for a Writ of

Certiorari] at 12 (Brief in Opposition). But the cases above

do not follow such a pattern. Nor did they all involve “bells

that could not be unrung.” No one would want the wrong

court to assign parental rights, but nothing would have

prevented World-Wide or Bandini from presenting their

federal arguments to this Court at the end of litigation

in the state system.

3. See also Rescue Army v. Municipal Court, 331 U.S. 549,

566 (1947) (describing Bandini’s view of this Court’s jurisdiction

as “well settled”); Madruga v. Superior Court, 346 U.S. 556, 557

n.1 (1954) (“The State Supreme Court’s judgment finally disposing

of the writ of prohibition is a final judgment reviewable here under

28 U.S.C. § 1257.”).

6

This Court also has jurisdiction under the fourth

category of Cox Broadcasting Corp. v. Cohn. See 420 U.S.

469, 482-83 (1975). The decision below rejected petitioners’

claim of federal preemption; reversal by this Court on

that issue would terminate the litigation; and important

federal interests are at stake.

II. Federal Common Law Precludes Respondents’

Claims.

As this Court knows, Erie Railroad Co. v. Tompkins

put an end to “federal general common law.” 304 U.S.

64, 78 (1938) (emphasis added). But some cases, by their

nature, cannot be governed by state law. This includes

situations where two or more sovereigns of equal

dignity lay claim to the same resource. Where this is

the case, federal specific common law controls. As this

Court recognized in Texas Industries, Inc. v. Radcliff

Minerals, Inc., federal common law governs “interstate

and international disputes implicating the conflicting

rights of States or our relations with foreign nations.”

451 U.S. 630, 641 (1981) (emphasis added). This “‘new’

federal common law addresses ‘subjects within national

legislative power where Congress has so directed’ or

where the basic scheme of the Constitution so demands.”

American Electric Power Co., Inc. v. Connecticut, 564

U.S. 410, 421 (2011) (AEP) (quoting Henry J. Friendly, In

Praise of Erie—And of the New Federal Common Law,

39 N.Y.U. L. Rev. 383, 408 n.119, 421-22 (1964)).

This Court has often relied on this principle. In fact,

it did so the same day as Erie, in an opinion by Justice

Brandeis himself. See Hinderlider v. La Plata River &

Cherry Creek Ditch Co., 304 U.S. 92 (1938). Hinderlider

involved a claim to water in the La Plata River, which flows

7

from Colorado into New Mexico. Although both states

assigned water by priority of appropriation, a compact

between the two states contemplated an alternative

regime in times of shortage. In such circumstances, the

engineers of the two states could agree to “rotate[]” use

of waters between the states “in alternating periods.”

Id. at 97.

This set up a conflict. Under Colorado law, the Ditch

Company was “entitled to divert 39¼ cubic feet of water

per second, subject to five senior priorities aggregating

19 second feet,” with no allowance for administrative

adjustment. Id. at 98. In the summer of 1928, however, flow

fell to 57 cubic feet per second. Thus, if the senior users

took their share and the Ditch Company took as much of

its share as possible, no water would remain for users in

New Mexico, some of whose claims predated the Ditch

Company’s. See id. The engineers invoked the compact

and the Ditch Company’s gate was shut. See id. at 95. It

then brought an action to compel Hinderlider, Colorado’s

Engineer, to restore its access to water. The trial court

refused relief, but the Supreme Court of Colorado held in

its favor. See id. at 99.

For purposes of this case, the issue on appeal was

whether Colorado law could control. This Court made

clear that it could not:

The claim that on interstate streams the

upper State has such ownership or control of

the whole stream as entitles it to divert all the

water, regardless of any injury or prejudice to

the lower State, has been made by Colorado in

8

litigation concerning other interstate streams,

but has been consistently denied by this Court.

Id. at 102.

An earlier case in this vein is Kansas v. Colorado,

206 U.S. 46 (1907). Like Hinderlider, this dispute arose

over a river (the Arkansas) that flowed from one state

(Colorado) into another (Kansas). Unlike in Hinderlider,

however, the two states had disparate approaches to water

rights. Whereas Colorado relied upon prior appropriation,

Kansas relied on the older riparian rule, which imposes

various restraints on diversion for agricultural purposes.

If Kansas could impose its rule on Colorado, much of the

water diverted in Colorado would have had to stay in the

river. If, by contrast, Colorado could impose its rule on

Kansas, then relatively little water would have remained

in the river for use downstream. Given the situation, the

only solution was a rule of federal common law. As the

Court observed:

One cardinal rule, underlying all the

relations of the States to each other, is that

of equality of right. Each State stands on the

same level with all the rest. It can impose its

own legislation on no one of the others, and is

bound to yield its own views to none.

Id. at 97. If the two states were “absolutely independent

nations,” the Court went on to note, their dispute could be

settled “by treaty or force.” But, “[n]either of these ways

being practicable, it must be settled by decision of this

court.” Id. at 98. The Court ultimately held for Colorado,

reasoning that the water went to greater use there than in

9

Kansas. See id. at 117. The key point, however, is not what

happened to the water, but what law controlled. Although

Colorado won the case, the governing law, in the words of

this Court, was something that “may not improperly be

called interstate common law.” Id. at 98.

Hinderlider and Kansas v. Colorado could be called

“apportionment cases” rather than “environmental cases,”

but the point is the same. In both situations, two or

more jurisdictions of equal dignity lay claim to the same

resource, be it water as a factor in agriculture or water

as a solvent or conduit for impurities. To be sure, water

as a factor in agriculture is measured simply by volume

and rate of flow, whereas water as a solvent is measured

by more abstract chemical principles, some of which may

be subject to debate, but the idea is the same. A single

resource is at stake and the players have equal standing.

No one player’s rules can control.

Accordingly, in Illinois v. City of Milwaukee, a dispute

over pollution rather than irrigation, this Court famously

declared the rule that controls the instant case: “When

we deal with air and water in their ambient or interstate

aspects there is a federal common law.” 406 U.S. 91, 103

(1972) (Milwaukee I). In Milwaukee I, Illinois tried to

bring an original action in this Court to abate discharges

into Lake Michigan by Milwaukee and other Wisconsin

defendants. See id. at 93. Although the Court remitted

the state to federal district court, see id. at 108, it was

abundantly clear that federal common law would control:

It may happen that new federal laws and

new federal regulations may in time pre-empt

the field of federal common law of nuisance.

10

But until that comes to pass, federal courts

will be empowered to appraise the equities of

the suits alleging creation of a public nuisance

by water pollution. While federal law governs,

consideration of state standards may be

relevant.

Id. at 107 (footnote omitted).

The instant case is a hypertrophic version of

Milwaukee I. Instead of one state facing off against

several subdivisions or instrumentalities of another

state over access to a single body of water, subdivisions

of Colorado are facing off against the rest of the United

States, and the world, over access to the global upper

atmosphere. But the principle is the same as in Milwaukee

I, Hinderlider, and Kansas v. Colorado: where sovereigns

of equal dignity lay claim to the same resource, the laws

of no one sovereign can control. Instead, the dispute must

be resolved at a higher level of law, such as by a treaty of

the United States, an act of Congress, or a rule of federal

common law. See U.S. Const. art. VI, cl. 2. Just as Colorado

could not impose its law on New Mexico in Hinderlider

or on Kansas in Kansas v. Colorado, and just as Illinois

could not impose its law on Milwaukee in Milwaukee I,

so too here Colorado may not impose its law of nuisance

or trespass on the rest of the United States or the world.

Respondents may argue that they seek only damages,

not to impose the laws of Colorado outside Colorado. See

Brief in Opposition at 3. But this is not true in function or

in fact. This Court has recognized that “‘regulation can

be . . . effectively exerted through an award of damages,’

and ‘[t]he obligation to pay compensation can be, indeed

11

is designed to be, a potent method of governing conduct

and controlling policy.’” Kurns v. R.R. Friction Prods.

Corp., 565 U.S. 625, 637 (2012) (quoting San Diego Bldg.

Trades Council v. Garmon, 359 U.S. 236, 247 (1959)). In

other words, the remedy respondents seek is every bit

as regulatory and interjurisdictional as an interstate

or international tax on fossil fuels. And at least one of

their counsel has acknowledged this, describing the

remedy respondents seek as a “carbon tax.” Brief for the

Petitioners at 38.

The effects of respondents’ action for damages, if

successful, are not hard to discern. First, the price of

petitioners’ products would go up everywhere petitioners

do business. To be sure, the degree of inflation would

depend on elasticity of demand, and petitioners’

shareholders would absorb some of the impact. But no

economist would deny that the supply curve for petitioners’

products would move up and to the left, raising prices

and reducing consumption. This is the “carbon tax” to

which one of respondents’ counsel referred. Second, to the

extent petitioners’ shareholders absorbed the impact of

respondents’ action, the price of petitioners’ stock would

fall, deterring investment and reducing petitioners’ ability

to raise capital in the equity markets. Third, creditors

would demand a premium before lending to petitioners,

given their exposure not only to respondents’ suit, but

also to similar suits if respondents’ action were allowed

to go forward.

In fact, if respondents’ action were allowed to go

forward, similar actions would proceed not only against

petitioners but also against other producers, and not only

in Colorado but in many other states. Ultimately, this

12

would have a global effect on the price of fossil fuels, on

demand for such products, and on petitioners’ access to

equity and debt markets, given the mobility of fossil fuels

and capital. In fact, the aggregate damages sought in these

actions could pose an existential threat to petitioners and

similar producers, pushing them toward bankruptcy. This

too one of respondents’ counsel has publicly acknowledged.

See Brief for the Petitioners at 38.

Respondents contend that they do not seek to base

liability on emissions, but only on the production and

sale of fossil fuels. See Brief in Opposition at 3. This is a

distinction without a difference. The harms they allege

in their complaint are keyed to emissions, not production

and sales. The Second Circuit got it right. “Artful pleading

cannot transform [respondents’] complaint into anything

other than a suit over global greenhouse gas emissions.

It is precisely because fossil fuels emit greenhouse

gases . . . that [they are] seeking damages.” City of New

York v. Chevron Corp., 993 F.3d 81, 91 (2021). Although

Respondents repeatedly describe their allegations as

“marketing” claims, see, e.g., Brief in Opposition at 3,

they do not sue for fraud, which is a tort in Colorado. See

M.D.C./Wood, Inc. v. Mortimer, 866 P.2d 1380, 1382 (Colo.

1994). Nor do they allege anywhere in their complaint

that anyone ever relied on any of petitioners’ alleged

misrepresentations, although reliance is an element of that

cause of action. See id. A search of the complaint for the

word “rely” or any of its cognates will not yield a single

allegation of this nature.

Relatedly, respondents describe federal common law

and the structure of the Constitution as non-overlapping

sources of legal authority on which petitioners have relied at

13

different stages of this litigation, implying that petitioners

are throwing arguments against the wall. See, e.g., Brief

in Opposition at 1 (describing petitioners’ arguments as

“ever-evolving”). This is unavailing. Federal common

law and the structure of the Constitution are not distinct

sources of authority. They are two sides of the same coin,

at least where Congress has not mandated common law

by statute. Precisely because we have a federal system

in which states do not invade each other over natural

resources, and precisely because no one state’s law can

control such disputes, the structure of the Constitution

demands a controlling rule of federal law. Whether

that rules comes from a treaty, an act of Congress, or

federal common law is beside the point. This Court has

repeatedly made this observation. In Massachusetts v.

Environmental Protection Agency, for example, it noted

that, “[w]hen a State enters the Union, it surrenders

certain sovereign prerogatives. Massachusetts cannot

invade Rhode Island to force reductions in greenhouse

gas emissions. . . .” “These sovereign prerogatives,” it

wrote, “are now lodged in the Federal Government. . . .”

549 U.S. 497, 519 (2007). “It may be imagined,” this Court

similarly observed in Missouri v. Illinois, “that a nuisance

might be created by a State upon a navigable river like

the Danube, which would amount to a casus belli for a

State lower down, unless removed. If such a nuisance were

created by a State upon the Mississippi the controversy

would be resolved by the more peaceful means of a suit

in this court.” 200 U.S. 496, 520-21 (1906).

Si mi la rly, respondents accuse petitioners of

contradicting themselves because, on the one hand,

they quote language from this Court describing federal

common law as “uniform,” yet, on the other, recognize

14

that Congress has power to preserve state law when it

displaces federal common law. See Brief in Opposition at

29. They are attacking a straw man. Although this Court

has often recognized that pragmatism might necessitate

a uniform rule of federal common law, see United States

v. Kimbell Foods, Inc., 440 U.S. 715, 728-29 (1979);

Clearfield Trust Co. v. United States, 318 U.S. 363, 367

(1943), nothing prevents Congress from both displacing

federal common law and allowing some state rules to

control. International Paper Co. v. Ouellette turned on

this point. “Although Congress intended to dominate

the field of pollution regulation,” this Court observed,

“the savings clause [of the Clean Water Act] negates the

inference that Congress ‘left no room’ for state causes

of action.” 479 U.S. 481, 492 (1987). This is also how the

Dormant Commerce Clause works. Although courts will

enjoin attempts by states to protect local commerce from

interstate competition, Congress itself is free to authorize

precisely such behavior. See, e.g., Northeast Bancorp,

Inc. v. Board of Governors of the Fed. Reserve Sys., 472

U.S. 159, 174 (1985) (“When Congress so chooses, state

actions which it plainly authorizes are invulnerable to

constitutional attack under the Commerce Clause.”).

III. Rescission of the Endangerment Finding Does Not

Alter the Outcome of This Case.

The Environmental Protection Agency’s decision to

rescind the Endangerment Finding is certainly relevant

to this case. See Rescission of the Greenhouse Gas

Endangerment Finding and Motor Vehicle Greenhouse

Gas Emission Standards Under the Clean Air Act, 91

Fed. Reg. 7686 (Feb. 18, 2026). But whatever the effect of

the rescission, and however it stands up to challenge, see,

15

e.g., Am. Pub. Health Ass’n v. U.S. Envtl. Prot. Agency,

D.C. Cir., No. 26-1037 (petition filed Feb. 18, 2026), the

outcome here is the same. If the Clean Air Act does not

“speak directly” to greenhouse gases, AEP, 564 U.S.

at 424 (cleaned up), then federal common law controls,

precisely as it did in Hinderlider, Kansas v. Colorado,

and Milwaukee I, because no one state’s law may govern

a dispute between sovereigns of equal dignity. Meanwhile,

if the Act does speak directly to greenhouse gases, then

the interaction of federal common law and the Act would

equally preempt those claims, because nothing in the Clean

Air Act displaces the structural truth that sovereigns of

equal dignity cannot impose their laws on each other. To

be sure, Congress can allow one state’s law to control,

but that requires an affirmative statement on Congress’

part, as this Court recognized in Ouellette. See 479 U.S. at

492. But there is no statement in the Act that would allow

Colorado to impose its law on any jurisdiction other than

Colorado, and nothing in respondents’ complaint indicates

that they are limiting their claims to conduct in that state.

Respondents contend that the conventional presumption

against preemption applies, but the circumstances of this

case preclude that possibility. Where, as here, a federal

statute displaces a body of federal common law that itself

was broadly preclusive for structural reasons, that broad

preclusion survives, and only an affirmative act of Congress

could provide otherwise. In other words, the presumption

in this context flips to one in favor of preemption. This

is not at all unusual. As this Court explained in United

States v. Locke, there are certain areas where “there is

no beginning assumption that concurrent regulation by

the State is a valid exercise of its police powers.” 529 U.S.

89, 108 (2000). That would include areas where, as here,

16

our constitutional structure prevents sovereigns of equal

dignity from imposing their laws upon each other, absent

authority from Congress.

IV. No Court and No Jury Could Feasibly Address

Respondents’ Allegations.

A final, cogent reason for this Court to reverse lies

in the fact that what respondents are asking the courts

of Colorado to do is beyond the institutional capacity

of any court. Colorado’s law of nuisance, like the law of

nuisance generally, asks courts (or juries) to compare the

social burdens and benefits of the defendant’s allegedly

tortious conduct. See City of Denver v. Mullen, 3 P. 693,

699 (Colo. 1884) (asking if the use is “reasonable”); Public

Serv. Co. v. Van Wyck, 27 P.3d 377, 391 (Colo. 2001) (citing

Restatement (2d) of Torts § 826, cmt. d) (asking the trier

of fact to “weigh the gravity of the harm and the utility

of the conduct causing that harm”).4 This may be feasible

where the neighbors of a cement plant allege injury from

the plant’s “dirt, smoke and vibration.” Boomer v. Atlantic

Cement Co., Inc., 26 N.Y.2d 219, 222 (1970). Experts could

perhaps testify to the value of the facility as a going

concern, its importance to the community and the local

economy, and the diminution in value of nearby property

due to its activities.

4. Colorado’s law of trespass, on its face, does not appear

to call for a comparison of the social benefits and burdens of

defendant’s activities. See Hoery v. United States, 64 P.3d 214,

217 (Colo. 2003). On the other hand, necessity is generally seen as

an affirmative defense to civil trespass, see Vincent v. Lake Erie

Transp. Co., 124 N.W. 221, 222 (Minn. 1910), which would appear

to return the trier of fact to a comparison of fossil fuel’s social

benefits and burdens.

17

But respondents’ case bears no resemblance to such

a local phenomenon, limited as it is to a single airshed

and relatively discrete vectors of injury. In fact, a judge

or jury hearing respondents’ case would have no greater

prospect of getting the right answer than central planners

would have in running an entire economy. We have seen

this movie before and we know how it ends. The calculus

is just too complex. As one economist noted:

Both central economic planning and judging

on wealth-maximizing or related utilitarian

g rou nds suppla nt a pr ice syst em w it h

centralized, non-price direction. To get decisions

right, therefore, both planners and courts must

act as if they compute relative prices and

estimate marginal utilities. The computation

problem, however, exceeds human capacity.

Peter H. Aranson, The Common Law as Central Economic

Planning, 3 Const. Pol. Econ. 289, 299 (1992).

In fact, what respondents are asking the courts of

Colorado to do is even harder than this. For not only are

the factors on either side of the equation beyond number;

they are measured in incommensurate units. As Justice

Gorsuch observed in National Pork Producers Council

v. Ross, answering questions like these is like trying to

“decide ‘whether a particular line is longer than a particular

rock is heavy.’” National Pork Producers Council v. Ross,

598 U.S. 356, 381 (2023) (Gorsuch, J.) (quoting Bendix

Autolite Corp. v. Midwesco Enterprises, Inc., 486 U.S.

888, 897 (1988) (Scalia, J., concurring in judgment)). See

also James M. Buchanan, Positive Economics, Welfare

Economics, and Political Economy, 2 J. L. & Econ. 124, 126

18

(1959) (“‘Efficiency’ in the sense of maximizing a payoff or

outcome from the use of limited resources is meaningless

without some common denominator, some value scale,

against which various possible results can be measured.”).

Many such riddles are present here. To give one

example, are the geopolitical advantages of having a

secure source of cheap, transportable energy greater or

less than the advantages of having less carbon dioxide in

the atmosphere? Liquified natural gas and petroleum can

be shipped and transshipped all over the world, protecting

nations from episodic threats. We saw this during the

invasion of Ukraine, when Europe pivoted from Russia

to the United States for natural gas. See Tom Fairless,

European Businesses Weathered War Storm, Wall St.

J., Mar. 25, 2023, at A8 (“One year [after the invasion],

many European companies have overcome the blow after

slashing energy use and pivoting to a friendly and booming

U.S. market.”).

To give a second example, are the socioeconomic

advantages of broad access to meaningful blue-collar

work greater or less that the advantages of having less

carbon dioxide in the atmosphere? Jobs matter, in both

financial and non-financial terms, and they may depend on

the availability of cheap, reliable energy. As one scholar

has noted, “[s]elf-identities cannot easily be attained on a

symbolic level alone; rather, they must be grounded in the

actual doing of social tasks.” Andrew J. Cherlin, Labor’s

Love Lost: The Rise and Fall of the Working-Class Family

in America 174 (2014). See also William Julius Wilson,

When Work Disappears: The World of the New Urban

Poor 73 (1996) (“In the absence of regular employment,

life, including family life, becomes less coherent.”).

19

Fossil fuels also contribute immensely to human

flourishing, enabling people to enjoy a standard of life that

might otherwise be impossible. Respondents may argue

that people in the developed world are at an inflection

point between fossil fuels and renewables, such that they

could flourish without fossil fuels, but this is far from

clear. An increase in the price of energy in London, for

example, has induced many people there not to resort to

wind and solar, but instead to burn wood. See Stephen

Castle, Why London’s Chimney Sweeps Are Enjoying

a Resurgence, N.Y. Times, Jan. 18, 2026 (“According to

the National Association of Chimney Sweeps, demand

[for their services] has been bolstered by high energy

prices, the popularity of wood-burning stoves and an

international climate that has prompted warnings that

electricity supplies could be vulnerable to attack by hostile

states like Russia.”). And many people in the developing

world are quite clearly at the inflection point between

fossil fuels, on the one hand, and such traditional sources

of energy as wood, on the other. See International Energy

Agency, A Vision for Clean Cooking Access for All at 3

(2023) (“[N]early one third of people around the world

cook their meals with rudimentary methods. They burn

coal, firewood, and even animal dung as fuel, breathing

in hazardous fumes daily.”). The people of the United

States are certainly allowed to care about people in the

developing world, even if they are not required to do so. See

Tibor Scitovsky, Two Concepts of External Economies, 62

J. Pol. Econ. 143, 144 (1954) (noting that “[t]he individual

person’s satisfaction may depend not only on the quantities

of products he consumes and services he renders but also

on the satisfaction of other persons”). The fact that we

are willing to spend billions of dollars per year for public

20

assistance demonstrates that we put a high value on the

happiness of others.

For a fourth example, who knows what benefits

artificial intelligence may bestow on the human race,

dependent as AI is, at least today, on vast amounts of

cheap, reliable energy. Just as fossil fuels sharply reduce

the amount of time people have to devote to gathering

energy, so too artificial intelligence offers the prospect

of giving millions, and perhaps billions, of people a head

start on practically every intellectual problem.

The point is not that fossil fuels easily win these

comparisons. The point instead is that these are

extraordinarily complex questions that lie beyond the

institutional capacity of judges and juries. Instead, they

lie with Congress, which reconstitutes the polity in all its

heterogeneity. Congress has 535 voting members, none

of whom reports to any other, and each of whom has an

inalienable role in the legislative process. If Congress

decided to impose a tax on fossil fuels, or to appropriate

money to enable jurisdictions like Boulder to absorb the

asserted costs of global warming, the people by their

representatives would have chosen that course of action.

And, unlike courts, Congress is not doctrinally bound to

do what would be impossible here—to get the calculus

right. This proposition is especially telling to the extent

respondents’ claims would regulate foreign emissions,

given the political branches’ exclusive responsibility for

foreign policy. Cf. Jesner v. Arab Bank, PLC, 584 U.S.

241, 265 (2018) (litigation under the Alien Tort Statute)

(“The political branches, not the Judiciary, have the

responsibility and institutional capacity to weigh foreignpolicy concerns.”).

21

CONCLUSION

For the foregoing reasons, amicus curiae respectfully

urges this Court to reverse the decision below.

Respectfully submitted,

Paul E. Salamanca

Counsel of Record

279 Cassidy Avenue

Lexington, KY 40502

(859) 338-7287

psalaman20@gmail.com

Counsel for Amicus Curiae