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 SENATORS TED CRUZ, CHUCK

GRASSLEY, MIKE LEE, AND TED BUDD AS

AMICI CURIAE IN SUPPORT OF

PETITIONERS

__________________________________________

CHARLES J. COOPER

Counsel of Record

ADAM P. LAXALT

BRADLEY L. LARSON

COOPER & KIRK, PLLC

1523 New Hampshire

Avenue, N.W.

Washington, D.C. 20036

(202) 220-9600

ccooper@cooperkirk.com

Counsel for Amici Curiae

May 21, 2026

i

TABLE OF CONTENTS

PAGE

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

INTEREST OF AMICI ................................................ 1

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

ARGUMENT ............................................................... 4

I.

The Extraterritorial-Regulation Doctrine

Bars Boulder’s Suit. .................................... 4

A. The Nature and Origin of the

Extraterritorial-Regulation Doctrine. ... 4

B. The Extraterritorial-Regulation

Doctrine Prohibits this Lawsuit. ......... 14

1.

Boulder’s Lawsuit Seeks to

Apply Colorado Law to Actions

Taken Outside of Colorado. .... 15

2.

This Court’s Foreign Affairs

Cases Confirm that

Boulder’s Lawsuit Is

Unconstitutional. .................... 19

II.

This Lawsuit Cannot Proceed as a

Regulation of Greenhouse-Gas

Emissions. .................................................. 23

III.

Conclusion ................................................. 29

ii

TABLE OF AUTHORITIES

CASES

PAGE(S)

Alden v. Maine,

527 U.S. 706 (1999) ......................................... 9, 10

Am. Elec. Power Co. v. Connecticut,

564 U.S. 410 (2011) ................................. 19, 24, 26

Am. Ins. Ass’n v. Garamendi,

539 U.S. 396 (2003) ............................................. 20

Barry v. Edmunds,

116 U.S. 550 (1886) ............................................. 22

Bell v. Cheswick Generating Station,

734 F.3d 188 (3d Cir. 2013) ................................ 29

BMW of N. Am., Inc. v. Gore,

517 U.S. 559 (1996) ......................................... 3, 22

Bonaparte v. Tax Court,

104 U.S. 592 (1881) ................................... 2, 11, 17

Burnham v. Super. Ct. of Calif., Cnty. of Marin,

495 U.S. 604 (1990) ....................................... 13, 14

Burrage v. United States,

571 U.S. 204 (2014) ............................................. 18

Chevron U.S.A. Inc. v. Echazabal,

536 U.S. 73 (2002) ............................................... 27

Chisholm v. Georgia,

2 Dall. 419 (1793) ................................................ 10

City & Cnty. of Honolulu v. Sunoco LP,

537 P.3d 1173 (Haw. 2023) ................................. 25

City of Milwaukee v. Illinois & Michigan,

451 U.S. 304 (1981) ............................................. 24

iii

City of New York v. Chevron Corp.,

993 F.3d 81 (2d Cir. 2021) .......... 23, 24, 25, 27, 29

Franchise Tax Bd. of Calif. v. Hyatt,

587 U.S. 230 (2019) ............................. 2, 5, 8, 9, 10

Fuld v. PLO,

606 U.S. 1 (2025) ............................................. 6, 20

Geier v. Am. Honda Motor Co.,

529 U.S. 861 (2000) ............................................. 25

Georgia v. Tenn. Copper Co.,

206 U.S. 230 (1907) ....................................... 23, 24

Hines v. Davidowitz,

312 U.S. 52 (1941) ............................................... 25

Holmes v. Sec. Inv. Protection Corp.,

503 U.S. 258 (1992) ............................................. 18

Hoyt v. Sprague,

103 U.S. 613 (1880) ................................. 4, 5, 6, 11

Huntington v. Attrill,

146 U.S. 657 (1892) ....................................... 11, 12

Illinois v. City of Milwaukee,

406 U.S. 91 (1972) ......................................... 23, 24

Int'l Paper Co. v. Ouellette,

479 U.S. 481 (1987) ........................... 23, 27, 28, 29

Japan Line, Ltd. v. County of Los Angeles,

441 U.S. 434 (1979) ............................................. 21

Kansas v. Colorado,

185 U.S. 125 (1902) ........................................... 8, 9

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

565 U.S. 625 (2012) ............................................. 21

iv

McIlvaine v. Coxe's Lessee,

4 Cranch 209 (1808) .............................................. 7

Minn. ex rel Ellison v. Am. Petroleum Inst.,

63 F.4th 703 (8th Cir. 2023) ......................... 23, 24

Movsesian v. Victoria Versicherung AG,

670 F.3d 1067 (9th Cir. 2012) ............................. 20

Murphy v. Nat’l Collegiate Athletic Ass’n,

584 U.S. 453 (2018) ............................................... 2

Nevada v. Hall,

440 U.S. 410 (1979) ............................................... 9

N.Y. Life Ins. Co. v. Head,

234 U.S. 149 (1914) ............................................. 11

Nat’l Pork Producers Council v. Ross,

598 U.S. 356 (2023) ....... 4, 5, 12, 14, 15, 16, 17, 19

Picquet v. Swan,

19 F.Cas. 609 (C.C.D. Mass. 1828) ..................... 13

Potter v. Allin,

2 Root 63 (Conn. Super. Ct. 1793) ...................... 13

Printz v. United States,

521 US 898 (1997) ......................................... 10, 11

Rhode Island v. Massachusetts,

12 Pet. 657 (1838) ................................................. 8

Scharfield v. Richardson,

133 F.2d 340 (D.C. Ct. App. 1942)...................... 26

Shelby County v. Holder,

570 U.S. 529 (2013) ....................................... 19, 20

Strassheim v. Daily,

221 U.S. 280 (1911) ..... 2, 12, 13, 14, 15, 17, 18, 19

v

The Schooner Exch. v. McFaddon,

11 U.S. 116 (1812) ......................................... 5, 6, 9

Whitman v. Am. Trucking Ass’ns,

531 U.S. 457 (2001) ............................................. 27

World-Wide Volkswagen Corp. v. Woodson,

444 U.S. 286 (1980) ............................................. 12

Young v. Masci,

289 U.S. 253 (1933) ............................................... 2

Zschernig v. Miller,

389 U.S. 429 (1968) ......................................... 3, 20

CONSTITUTIONAL PROVISIONS AND CODES

U.S. CONST. art. I, § 8, cl. 10 ....................................... 8

U.S. CONST. art. II, § 2, cl. 2 ..................................... 21

42 U.S.C.

§ 7416 ............................................................ 27, 28

§ 7604(e) .............................................................. 29

OTHER AUTHORITIES

1 JABEZ G. SUTHERLAND, A TREATISE ON THE

LAW OF DAMAGES (1882) ............................... 18, 19

4 WILLIAM BLACKSTONE, COMMENTARIES ON THE

LAWS OF ENGLAND (1769) ...................................... 6

13 JOHN P. KAMINSKI ET AL., THE DOCUMENTARY

HISTORY OF THE RATIFICATION OF THE

CONSTITUTION

(Wis. Hist. Soc’y Press, 1981) ........................... 7, 8

22 Memorandum from Timothy Bloodworth to the

North Carolina General Assembly Concerning

a Treaty Between the United States and Spain

(December 16, 1786) ............................................. 7

vi

Amended Compl., No. 18CV30359 (Dist. Ct.

Boulder Cnty., Colo. June 11, 2018)....... 15, 16, 22

Brief for Vermont, United States v. Vermont,

No. 2:25-cv-00463 (D. Vt. Nov. 17, 2025),

ECF No. 53 .......................................................... 12

BRUTUS NO. 13 (Feb. 21, 1788) .................................. 10

Decl. of Christopher Landau, United States v.

Vermont, No. 2:25-cv-00463 (D. Vt.),

ECF No. 50-3 ....................................................... 22

Katherine Florey, State Courts, State Territory, State

Power: Reflections on the Extraterritoriality

Principle in Choice of Law and Legislation,

84 NOTRE DAME L. REV. 1057 (2009) .................. 12

Progress Through Partnership, EXXON MOBIL,

https://perma.cc/5NDN-BR4Z ....................... 20, 21

Donald H. Regan, Siamese Essays: (I) CTS

Corp. v. Dynamics Corp. of America and

Dormant Commerce Clause Doctrine; (II)

Extraterritorial State Legislation,

85 MICH. L. REV. 1865 (1987) ................... 5, 12, 14

ANTONIN SCALIA & BRYAN A. GARNER, READING LAW:

THE INTERPRETATION OF LEGAL TEXTS (2012) .... 26

Stephen E. Sachs, Pennoyer Was Right,

95 TEXAS L. REV. 1249 (2017) ................. 6, 7, 9, 10

JOSEPH STORY, COMMENTARIES ON THE CONFLICT

OF LAWS (1834) .................................................. 4, 5

The Declaration of Independence (U.S. 1776) ............ 7

THE FEDERALIST NO. 42

(James Madison) ................................... 3, 7, 20, 22

THE FEDERALIST at NO. 44 (James Madison) ........... 20

vii

THE FEDERALIST NO. 80 (Alexander Hamilton) .... 7, 24

EMER DE VATTEL, THE LAW OF NATIONS (1758) ...... 5, 6

1

INTEREST OF AMICI

Amici are Senators Ted Cruz, Chuck Grassley,

Mike Lee, and Ted Budd.1 As members of the branch

charged

with

formulating

our

country’s

environmental, energy, and national-security laws,

amici have an especially strong interest in the

outcome of this case. Allowing the Colorado Supreme

Court’s decision to stand would undermine the

structure of our constitutional system and create

significant tension between the United States and

foreign countries by allowing individual states to

create liability for actions taken exclusively within

foreign sovereigns’ territory.

SUMMARY OF THE ARGUMENT

Imagine a barrel of oil that is extracted from an

Exxon-owned well in Texas, refined into gasoline in

Texas, sold at a gas pump in Texas, and used to fuel

cars in Texas. Does our Constitution allow Colorado

tort law to impose liability on Exxon’s extraction of the

oil? The Colorado Supreme Court answered “yes.” At

the request of a handful of municipal governments in

Boulder, the Colorado Supreme Court ruled that

Colorado courts may apply Colorado law to drilling,

mining, refining, and advertising across the globe.

The Colorado Supreme Court is mistaken. The

Constitution—as evidenced by its structure and our

Nation’s

Founding-era

history—prohibits

the

application of Colorado law to activities taken outside

of Colorado and having no connection to the state.

1 No counsel for any party has authored this brief in whole

or in part, and no entity or person, aside from Amici’s counsel,

made any monetary contribution intended to fund the

preparation or submission of this brief.

2

Before the ratification of our Constitution, states

interacted effectively as foreign sovereigns. Under the

law of nations, a sovereign’s authority extended only

so far as its own territory. But because the law of

nations contained no centralized enforcement

mechanism, each sovereign could attempt to assert

global jurisdiction (although no other nation would

have to respect such assertion). The Constitution,

however, “affirmatively altered the relationships

between the States, so that they no longer relate to

each other solely as foreign sovereigns.” Franchise

Tax Bd. of Calif. v. Hyatt, 587 U.S. 230, 245 (2019);

see also Murphy v. Nat’l Collegiate Athletic Ass’n, 584

U.S. 453, 470 (2018) (“The Constitution . . . prohibits

the States from exercising some attributes of

sovereignty.”).

One

such

alteration

was

constitutionalizing the rule that a sovereign’s

authority only extended to its borders. As this Court

has explained, “[n]o state can legislate except with

reference to its own jurisdiction.” Bonaparte v. Tax

Court, 104 U.S. 592, 594 (1881).

Boulder seeks to violate this core tenet of

federalism by imposing its own tort law on fossil-fuel

production, refining, and advertising in other states

and, even more aggressively, in foreign countries.

Because Boulder attempts to directly regulate activity

outside of Colorado, it must show that the sole

exception to the Constitution’s extraterritorialregulations doctrine applies by demonstrating that (1)

Petitioners intended to create harm in Colorado and

(2) that their activities had a direct and traceable

connection to the relevant in-state harm. See

Strassheim v. Daily, 221 U.S. 280, 285 (1911); cf.

Young v. Masci, 289 U.S. 253, 259 (1933). Because

Boulder cannot allege that Petitioners intended to

3

create harm inside of Colorado and relies on the most

indirect effects of drilling imaginable—i.e., alleged

global temperature increases over the past century

based in part on the emissions from third parties

burning fossil fuels—it cannot extend its jurisdiction

to cover the entire globe.

It should not be surprising that the Constitution

prohibits Boulder from using Colorado law to appoint

itself as a worldwide Environmental Protection

Agency. In addition to limiting the power of states to

regulate activities in their sister states, the

Constitution vests the ability to conduct foreign

affairs in the federal government, Zschernig v. Miller,

389 U.S. 429, 432 (1968), because allowing 50 states

to wield such power would “embroil the Confederacy

with foreign nations,” THE FEDERALIST NO. 42 (James

Madison). The Framers were smart enough not to

allow juries, who speak for the “voice of the[ir]

community,” BMW of N. Am., Inc. v. Gore, 517 U.S.

559, 600 (1996) (Scalia, J., dissenting), to impose

liability on actions taken in a wholly different

community.

Even if Boulder could rely on the putative link

between the release of greenhouse gases and global

climate change to skirt the Constitution’s prohibition

on extraterritorial regulations, it would walk itself

into the preemptive force of the Clean Air Act.

Although Boulder disclaims that it seeks to create

liability for interstate (and international) air

pollution, its theory of liability necessarily rests on the

fact that air pollution from other jurisdictions is

causing it harm. The Clean Air Act, however, prevents

states from applying their own law to emissions from

other states.

4

Boulder cannot have things both ways. If Boulder

is attempting to apply Colorado law to out-of-state

production, refining, and advertising of fossil fuels,

then it fails to state a claim because of the

extraterritorial-regulations doctrine. If Boulder is

attempting to apply Colorado law to the emissions

produced by the eventual burning of the extracted

fuels by third parties, then Boulder fails to state a

claim because of the Clean Air Act. No matter how

Boulder formulates its theory or how this Court

understands it, there is no escape from the fact that

Boulder cannot sustain this suit under “Colorado

law.” Pet.App.6a.

ARGUMENT

I. The Extraterritorial-Regulation Doctrine

Bars Boulder’s Suit.

A. The Nature and Origin of the

Extraterritorial-Regulation Doctrine.

This Court has long recognized that the “general

legislative power of a State” extends so far as “to act

upon persons and property within the limits of its own

territory.” Hoyt v. Sprague, 103 U.S. 613, 630 (1880);

cf. JOSEPH STORY, COMMENTARIES ON THE CONFLICT OF

LAWS § 20 (1834) (“[N]o State or nation can, by its

laws, directly affect, or bind property out of its own

territory, or persons not resident therein.”). This basic

precept of federalism allows the states to serve as

laboratories of democracy, with no state being able to

override the legal choices of another. Although this

Court has applied the extraterritorial-regulation

doctrine in a wide variety of cases, it has yet to provide

an in-depth explanation for the doctrine’s origin and

nature. History reveals that the extraterritorial-

5

regulation doctrine is best understood—similar to a

state’s sovereign immunity outside the Eleventh

Amendment—as emanating from the very structure

of the Constitution itself. See Nat’l Pork Producers

Council v. Ross, 598 U.S. 356, 375 (2023); see also

Donald

H.

Regan, Siamese

Essays:

(I) CTS

Corp. v. Dynamics Corp. of America and Dormant

Commerce Clause Doctrine; (II) Extraterritorial State

Legislation, 85 MICH. L. REV. 1865, 1885 (1987) (“It is

one of those foundational principles of our federalism

which we infer from the structure of the Constitution

as a whole.”).

Before the Founding of our nation, a sovereign’s

powers were understood—under the law of nations—

to extend only throughout its territory. In the words

of Emmerich de Vattel, “the founding era’s foremost

expert on the law of nations,” Franchise Tax Bd., 587

U.S. at 239, each sovereign had the exclusive right to

“direct[] and regulate[] at its pleasure every thing that

passes in the country.” EMER DE VATTEL, THE LAW OF

NATIONS, ch. XVIII, § 204 (1758). And that “exclusive

right” necessarily excluded other sovereigns from

seeking to regulate the same conduct. Id. § 203; see

also Story, supra, § 20 (“[N]o State or nation can, by

its laws, directly affect or bind property out of its own

territory, or persons not resident therein.”). As Chief

Justice Marshall put it, “[t]he jurisdiction of the

nation within its own territory is necessarily

exclusive . . . .” The Schooner Exch. v. McFaddon, 11

U.S. 116, 136 (1812). Under the law of nations, each

sovereign “possess[ed] equal rights and equal

independence.” Id. If one sovereign wished to extend

its reach to govern events that took place in the

territory of another sovereign, the second sovereign

must “have consented” because the law of Nations

6

regarded each country as “being incapable of

conferring extra-territorial power” upon itself. Id. at

136–37; Hoyt, 103 U.S. at 630–31 (“[W]hatever force

and obligation the laws of one country have in

another, depend solely upon the laws of the latter,

that is, upon the comity exercised by it.” (citing Story,

supra, §§ 18–23)). If one sovereign sought to regulate

actions in the territory of another sovereign without

consent, no other nation would be obliged to respect

the assertion of jurisdiction. And the nation who

suffered the legal incursion had cause to demand

satisfaction and, if not satisfied, engage in war. See 4

WILLIAM BLACKSTONE, COMMENTARIES ON THE LAWS

OF ENGLAND 68 (1769). Because no sovereign had

“superior jurisdiction” to bring the case before a

tribunal, diplomacy and violence were the only routes

to resolve the conflict. Id.

In the era immediately preceding the Founding,

the rules for determining the regulatory jurisdiction

of sovereigns were simple. Sovereigns had plenary

authority to regulate the actions taking place within

their territory. Vattel, supra, § 204; The Schooner

Exch., 11 U.S. at 136. If a sovereign wished to regulate

events within another sovereign’s territory, the law of

nations required consent (whether explicit or

implied). Hoyt, 103 U.S. at 630–31. A sovereign state

could proceed to violate the law of nations and assert

worldwide jurisdiction without consent. See Fuld v.

PLO, 606 U.S. 1, 35–36 (2025) (Thomas, J., concurring

in the judgment) (explaining that limits on

“extraterritorial jurisdiction,” which “stemmed from

general principles of international law” could be

“override[n] through clear command” of a sovereign).

If a sovereign elected to “override” the territorial

limitations on its authority, id., however, other

7

sovereigns would not be obligated to acknowledge

such

an

act

as

legitimate.

Stephen

E.

Sachs, Pennoyer Was Right, 95 TEXAS L. REV. 1249,

1270 (2017). Indeed, such a violation of the law of

nations could provide cause for lawful retaliation, up

to and including war. See Blackstone, supra, at 68.

Because each state was a fully separate sovereign

after they declared independence from England, The

Declaration of Independence para. 5 (U.S. 1776), these

rules governed their relationships between 1776 and

1789, see McIlvaine v. Coxe's Lessee, 4 Cranch 209,

212 (1808).

This system of international relations, however,

proved an awkward fit under the Articles of

Confederation. Because the Articles “contain[ed] no

provision for the case of offenses against the law of

nations,” each state determined for itself when the

law of nations was violated. THE FEDERALIST NO. 42

(James Madison). And because the states were now

part of a league, that interpretive power meant that

one state could draw the others into conflict. In the

words of James Madison, the Articles of

Confederation allowed a single “indiscreet member to

embroil the Confederacy with foreign nations.” Id.;

THE FEDERALIST NO. 80 (Alexander Hamilton) (“[T]he

peace of the WHOLE ought not to be left at the

disposal of a PART”). This risk was not speculative.

After the Revolutionary War, the Spanish closed off

navigation of the Mississippi River to Americans.

Southern states viewed that action as violating their

right under the law of nations to navigate the river.

See 22 Memorandum from Timothy Bloodworth to the

North Carolina General Assembly Concerning a

Treaty Between the United States and Spain

(December 16, 1786). Indeed, there was talk of raising

8

a southern army and fighting the Spanish for control

of the Mississippi, which would have drawn the entire

nation into a war against its will. See 13 JOHN P.

KAMINSKI ET AL., THE DOCUMENTARY HISTORY OF THE

RATIFICATION OF THE CONSTITUTION 149–52 (Wis.

Hist. Soc’y Press, 1981). Luckily, tensions with the

Spanish diminished and war was averted, but the

incident made clear that allowing each state to act as

a sovereign in the international sphere was a recipe

for trouble.

Motivated by the failures under the Articles of

Confederation, the ratification of the Constitution and

creation of the federal government “affirmatively

altered the relationships between the States, so that

they no longer relate to each other solely as foreign

sovereigns.” Franchise Tax Bd., 587 U.S. at 245. For

example, Article I of the Constitution “divest[ed] the

States of the traditional diplomatic and military tools

that foreign sovereigns possess.” Id. Similarly, Article

IV imposed duties on states, such as honoring

extradition requests and judgments from other states,

that only existed as a matter of comity under the law

of nations. Id. And perhaps most importantly, Article

I gave Congress the power to “define and punish . . .

Offenses against the Law of Nations,” taking that

power away from the States as Madison advocated in

Federalist 42. U.S. CONST. art. I, § 8, cl. 10.

The transition from a loose confederation of states

into a single nation transformed the law governing

many subjects. Some areas which were previously

governed by the law of nations, which was enforced

through diplomacy and violence, became governed by

constitutional restrictions on state power, which are

enforced through “rules of law” applicable in

9

courts. Rhode Island v. Massachusetts, 12 Pet. 657,

737 (1838); Kansas v. Colorado, 185 U.S. 125, 143

(1902) (“[T]he Constitution does not contemplate that

controversies between members of the United States

may be settled by reprisal or force of arms.”). For

instance, before the ratification of the Constitution,

whether one state could hale another state (or any

other sovereign) into its courts was a matter of comity

under the law of nations. See The Schooner Exch., 11

U.S. at 136; Alden v. Maine, 527 U.S. 706, 713 (1999)

(“[T]he States’ immunity from suit is a fundamental

aspect of the sovereignty which the States enjoyed

before the ratification of the Constitution.”). But the

Constitution made that rule into one of constitutional

significance. See Franchise Tax Bd., 587 U.S. at 249

(overruling Nevada v. Hall, 440 U.S. 410 (1979));

Nevada v. Hall, 440 U.S. at 439–42 (Rehnquist, J.,

dissenting); Alden, 527 U.S. at 713 (describing how

the Constitution’s “structure” and “history” evince an

intent to constitutionalize sovereign immunity).

Similarly, before the ratification of the Constitution, a

dispute about a state’s borders was decided through

“raw power.” Franchise Tax Bd., 587 U.S. at 246. But

after the enactment of the Constitution, such a

dispute would be decided under principles of federal

law. Id.

The law-of-nations rule that one sovereign cannot

regulate actions in the territory of another sovereign

was another doctrine the Constitution transformed

into a court-enforceable rule. Cf. Sachs, supra, at 1253

(explaining that “federal courts” would give “no more

weight to laws asserting jurisdiction beyond state

borders than to laws purporting to redraw those

10

borders themselves”).2 Like sovereign immunity, its

application was necessary to avoid the kind of “direct

conflict between sovereigns” that the Constitution

took out of the states’ hands. Franchise Tax Bd., 587

U.S. at 246–47. If anything, the constitutionalization

of the extraterritorial-regulation doctrine was even

better established than sovereign immunity at the

founding. One could have argued—as the

Antifederalists did—that the grant of jurisdiction over

lawsuits involving states in Article III abrogated

sovereign immunity. See BRUTUS NO. 13 (Feb. 21,

1788) (objecting to Article III “because it subjects a

state to answer in a court of law[] to the suit of an

individual”). Indeed, this Court incorrectly held so in

Chisholm v. Georgia, 2 Dall. 419 (1793), before the

people overturned that ruling through the Eleventh

Amendment. Given Article III’s verbiage and the

Antifederalist opposition, the issue of sovereign

immunity aroused robust debate when the people

decided whether to ratify the Constitution. See Alden,

527 U.S. at 717–19 (cataloguing the debates). Because

nothing in the Constitution implied that states could

regulate outside of their territory, however, there was

little reason to debate whether the Constitution

authorized such regulations.

Indeed, it is remarkable how well-settled the rule

against extraterritorial regulation appeared to be in

the aftermath of the Constitution. See Printz v. United

States, 521 US 898, 907–08 (1997) (explaining that

“the utter lack of statutes” exercising a power

“suggests an assumed absence of such power”

Professor Sachs made this comment in the context of

discussing personal jurisdiction and not regulatory jurisdiction,

but the same analysis applies.

2

11

(emphasis in original)). In the words of this Court, the

territorial restrictions on state power were “so

obviously the necessary result of the Constitution”

that such restrictions have “rarely been called in

question and hence authorities directly dealing with

it do not abound.” N.Y. Life Ins. Co. v. Head, 234 U.S.

149, 161 (1914). Even in the furious days leading up

to the Civil War, for example, no state sought to

extend its reach and regulate conduct in other states.

How easy it would have been for Massachusetts to

declare that slavery was illegal in Georgia and to

arrest any slaveowner that it could get its hands on.

Around a century after the ratification of the

Constitution, however, states began to expand the

reach of their laws to plausibly extend beyond their

borders. For example, in Bonaparte v. Tax Court of

Baltimore, 104 U.S. at 594, a bondholder claimed that

her bonds issued by various states were exempt from

taxation because they were universally “exempt from

taxation by the debtor State.” Id. This Court held the

line, concluding that states could not set tax policy for

bonds held outside of their own territory because

“[o]ne State cannot exempt property from taxation in

another.” Id. Indeed, in the decades surrounding the

turn of the 20th century, a myriad of cases came to

this Court and were decided on extraterritorialregulation grounds. See Hoyt, 103 U.S. at 630

(explaining that the “legislative power of a State to act

upon persons and property within the limits of its own

territory,” does not extend to “persons and property”

outside of its territory); see N.Y. Life Ins. Co., 234 U.S.

at 161 (“[I]t would be impossible to permit the statutes

of Missouri to operate beyond the jurisdiction of that

State.”); Huntington v. Attrill, 146 U.S. 657, 669

(1892) (“Laws have no force of themselves beyond the

12

jurisdiction of the state which enacts them, and can

have extraterritorial effect only by the comity of other

states.”). These cases, notably, did not rely on a

specific clause of the Constitution but accepted that

the very structure and nature of the Constitution

prohibited extraterritorial regulation. Nat’l Pork

Producers Council, 598 U.S. at 375 & 376 n.1

(reaffirming that the extraterritorial-regulation

doctrine emanates from the structure of the

Constitution and not one particular clause); Regan,

supra, at 1875–1880, 1897–1902 (explaining why no

single clause explains the extraterritorial-regulations

doctrine); Katherine Florey, State Courts, State

Territory, State Power: Reflections on the

Extraterritoriality Principle in Choice of Law and

Legislation, 84 NOTRE DAME L. REV. 1057, 1060 (2009)

(explaining that the extraterritoriality principle is “a

prohibition rooted in general structural principles of

horizontal federalism”).

Litigants who doubt the existence of the

extraterritorial-regulations doctrine point to other

provisions of the Constitution and claim that those

provisions exhaust all of the Constitution’s federalism

doctrine. Brief for Vermont, United States v. Vermont,

No. 2:25-cv-00463 (D. Vt. Nov. 17, 2025), ECF No. 53.

But as Professor Regan has explained, these doctrines

cannot explain the territorial limits on state power

both as a historical matter and as a matter of this

Court’s precedents. See, Regan, supra, at 1875–1880,

1897–1902. For example, this Court has often relied

on the Due Process Clause of the Fourteenth

Amendment to limit the ability of states to regulate

across borders through the use of personal

jurisdiction. E.g., World-Wide Volkswagen Corp. v.

Woodson, 444 U.S. 286, 291 (1980). But jurisdiction

13

over a person and the territorial scope of a state’s

jurisdiction are not the same. See Strassheim, 221

U.S. at 285.

The concept of “tag jurisdiction” shows how the

two concepts differ. If a person is served with process

while physically present in a state, that state has

personal jurisdiction over him. See Burnham v. Super.

Ct. of Calif., Cnty. of Marin, 495 U.S. 604, 610–11

(1990); Potter v. Allin, 2 Root 63, 67 (Conn. Super. Ct.

1793); Picquet v. Swan, 19 F.Cas. 609 (C.C.D. Mass.

1828) (Story, J.). It does not matter whether the

subject of the lawsuit has nothing else to do with that

state. Burnham, 495 U.S. at 610–11. But the existence

of personal jurisdiction only determines whether the

court may hear the case, it does not determine

whether that court may apply the law of the forum

state to purely out-of-state activities. This Court

explained as much in Strassheim. There, it explained

that a state may punish out-of-state conduct only if (1)

the conduct was “intended to produce and produc[ed]

detrimental effects within” the state, and (2) “the

state should succeed in getting him within its power.”

Strassheim, 221 U.S. at 285. The Court thus

distinguished between the scope of a state’s

regulatory authority and the ability of the state to

exercise personal jurisdiction over an individual.

A hypothetical illustrates the important

differences between personal jurisdiction and

territorial jurisdiction. Imagine that Georgia outlaws

sports gambling, not just in Georgia but across the

entire country (or even the world). Nevada resident

John Doe places a bet in a Las Vegas casino, where

sports gambling is legal, that the Las Vegas Golden

Knights will win their hockey game that night in Las

14

Vegas. A few months later, John travels to Georgia,

and the Georgia Attorney General properly serves

him with a civil enforcement action for violating

Georgia’s anti-gambling law by placing a bet in Las

Vegas. The Georgia courts would certainly have

personal jurisdiction over John because he was

present in Georgia when validly served. Burnham,

495 U.S. at 610–11. Yet it is equally obvious that

Georgia could not apply its own gambling law against

John for his lawful activities in Nevada, even though

Georgia succeeded “in getting him within its power”

through valid service.3 Strassheim, 221 U.S. at 285.

Although this Court has consistently held that the

“original and historical understandings of the

Constitution’s structure and the principles of

‘sovereignty and comity’ it embraces” prohibit states

from directly regulating conduct outside their borders,

it has allowed a narrow set of such laws to pass

constitutional muster. Nat’l Pork Producers Council,

598 U.S. at 376 (quoting BMW of N. Am., 517 U.S. at

572). If an action outside of a state was “intended to

produce and produc[ed] detrimental effects within”

the state, then the state can punish the person if it

“should succeed in getting him within its power.”

Strassheim, 221 U.S. at 285.

B. The Extraterritorial-Regulation

Doctrine Prohibits this Lawsuit.

Boulder’s attempt to hold Exxon and Suncor liable

for the extraction, refining, and advertising of fossilThis hypothetical is largely taken from Professor Don

Regan’s example of “the traveling Illinois homosexual” in his

seminal article on the nature of the extraterritorial-regulation

doctrine. Regan, supra, at 1892–93.

3

15

fuel products across the globe is impermissible under

the extraterritorial-regulation doctrine. Taking

Boulder and the Colorado Supreme Court at their

word, this lawsuit seeks to directly apply Colorado law

to actions that took place (and will take place) in other

states and countries. And the exception that allows a

state to apply its law to certain out-of-state activities

does not apply. Id.; Nat’l Pork Producers Council, 598

U.S. at 375–76.

1. Boulder’s Lawsuit Seeks to

Apply Colorado Law to Actions

Taken Outside of Colorado.

To understand why the Constitution does not

allow this lawsuit, it is important to understand

Boulder’s precise theory of liability. According to

Boulder, Suncor and Exxon have committed various

torts under Colorado law “by producing, promoting,

refining, marketing[,] and selling fossil fuels at levels

that have caused and continue to cause climate

change.” Pet.App.2a. Boulder also complains that

Petitioners will continue to commit these torts in the

future by failing to reduce their business footprints.

Amended Compl. ¶ 322, No. 18CV30359 (Dist. Ct.

Boulder Cnty., Colo. June 11, 2018) (Am. Compl.).

These actions, Boulder admits, did not take place

within Colorado. Instead, Boulder openly seeks to

establish liability for actions that took place in other

states and other countries.

The damages that Boulder seeks are those that it

believes are the result of global climate change, such

as “extreme hot summer days and increases in

minimum nighttime temperatures, precipitation

changes, larger and more frequent wildfires,

increased concentrations of ground-level ozone,

16

higher transmission of viruses and disease from

insects, altered stream-flows, bark beetle outbreaks,

ecosystem damage, forest die-off, reduced snowpack,

and drought.” Id. ¶ 140. These costs, and others,

amount to hundreds of millions of dollars within

Boulder alone. If Boulder’s theory comports with the

structural limits on the reach of Colorado law, every

single state and municipality in the country could

seek hundreds of millions or billions of dollars in

damages for the production of fossil fuels.

Boulder’s theory of liability, however, runs

headfirst into the extraterritorial-regulation doctrine.

It seeks to use Colorado law to “‘directly’” impose

liability on actions that took place in other states and

in foreign countries. Nat’l Pork Producers Council,

598 U.S. at 376 n.1 (quoting Edgar v. MITE Corp., 457

U.S. 624, 641 (1982)) (emphasis omitted). The

Colorado Supreme Court explained as much when it

concluded that Boulder’s claims target “defendants’

upstream production activities.”4 Pet.App.21a; Cert

Opp. at 26 (explaining that the lawsuit seeks to target

“inputs to emitting facilities”). Creating liability for

engaging in a specific activity is the paradigmatic

example of a “direct” regulation of that activity.

This Court recently illustrated the distinction

between a direct and an indirect regulation in Nat’l

Pork Producers Council. There, California enacted a

law that governed what kinds of pork could be sold in

grocery stores within California. Unless the pork

came from pigs raised under conditions that

California considered humane, it could not be sold in

As explained below, Boulder’s theory also relies on the

emission of greenhouse gases, which makes the suit preempted

by the Clean Air Act.

4

17

California grocery stores. Nat’l Pork Producers

Council, 598 U.S. at 365–66. Because California

makes up such a large percentage of the national pork

market, this regulation had the “practical effect” of

requiring pig farmers across the country to follow

California’s rules. Id. at 371. The petitioners in that

case did not (and could not) allege that California was

directly regulating how pigs were raised in other

states because the direct object of the regulation was

California supermarkets, which are clearly within

California’s regulatory jurisdiction. This Court went

to great pains to distinguish an extraterritorial

application of a state’s law (impermissible) and the

extraterritorial effect of a state’s law (permissible). Id.

at 373–74. As this Court implied, Pork Producers

would have presented a whole different question if

California had explicitly regulated practices in other

states instead of regulating “with reference to its own

jurisdiction,”

i.e.,

California

supermarkets.

Bonaparte, 104 U.S. at 594. Boulder’s lawsuit does not

seek to merely have the practical effect of regulating

out-of-state conduct, rather, it seeks to explicitly

establish liability for that conduct.

Because Boulder seeks to establish direct liability

on the extraction, sale, and other activities related to

fossil-fuel production that occur outside of Colorado, it

must demonstrate that Petitioners “intended to

produce and produc[ed] detrimental effects within”

the state. Strassheim, 221 U.S. at 285. Boulder cannot

do either.

First, Boulder’s Amended Complaint alleges

nothing about Petitioners’ intent to cause climaterelated harms in Boulder. To be sure, the Amended

Complaint makes allegations that Petitioners had

18

some knowledge of purported climate change in the

1970s and 1980s. But the alleged knowledge of some

form of climate change does not translate into intent

to create “detrimental effects within” Colorado. Id.

Because nothing in the complaint alleges that

Petitioners knew that their actions would cause harm

within Colorado, Boulder cannot use Colorado law to

seek damages for their out-of-jurisdiction conduct. Id.

Perhaps more importantly, Boulder’s complaint

does not—and could not—allege that the Petitioners’

activities have caused “detrimental effects within”

Colorado that would satisfy this exception. Id. At the

threshold, there are a handful of different ways that

this Court could analyze whether an out-of-state act

sufficiently “produc[ed] detrimental” effects to fall

outside of the extraterritorial-regulations doctrine.

Id.; Amicus Brief of the United States at 14 (stating

that there must be a “a direct and traceable

connection” between the out-of-state conduct and the

putative harm). The most obvious test to determine

the requisite causal nexus for the extraterritorial

extension of a state’s regulatory reach is something

similar to “‘legal’ cause.” Burrage v. United States, 571

U.S. 204, 210 (2014) (quoting 1 W. LAFAVE,

SUBSTANTIVE CRIMINAL LAW § 6.4(a), pp. 464–466 (2d

ed. 2003)). “‘[L]egal’ cause,” often referred to as

“‘proximate cause,’” id., requires the action of the

defendant to bear a sufficiently direct connection with

the harm alleged to be held liable for it. This Court

has repeatedly stated that for an individual to be

legally liable for some injury, there must have been

“some direct relation between the injury asserted and

the injurious conduct alleged.” Holmes v. Sec. Inv.

Protection Corp., 503 U.S. 258, 268 (1992); 1 JABEZ G.

19

SUTHERLAND, A TREATISE ON THE LAW OF DAMAGES

55–56 (1882).

The connection between Petitioners’ worldwide

“promoting, refining, marketing and selling” of fossil

fuels over a multi-decade period and specific

environmental effects in Colorado is so attenuated as

not to qualify under any standard of causation.

Emissions from an end user of fossil fuels cannot be

traced to any specific real-world harm. As this Court

has explained, “emissions in New Jersey may

contribute no more to flooding in New York than

emissions in China” Am. Elec. Power Co. v.

Connecticut, 564 U.S. 410, 422 (2011) (AEP). The

theory of liability that Boulder seeks to establish is

even more attenuated. It seeks liability for various

activities even earlier in the alleged causal chain

(drilling, refining, advertising, etc.) that occur not

only before the fossil fuels are burned, but before that

burning emits pollutants that allegedly combine in

the Earth’s atmosphere to cause changes in the

climate over decades. Putative global climate change

and the alleged attendant harms within Boulder are

the most “indirect” result imaginable from Petitioners’

extraction and refining of fossil fuels.

2. This Court’s Foreign Affairs

Cases Confirm that Boulder’s

Lawsuit Is Unconstitutional.

Boulder’s attempt to impose liability on actions

taken in other states is impermissible under “original

and historical understandings of the Constitution’s

structure,” Nat’l Pork Producers Council, 598 U.S. at

376, and this Court’s precedent analyzing that

structure, see Strassheim, 221 U.S. at 285. But

Boulder does not stop there. It seeks not only to extend

20

its jurisdiction to abridge the “equal sovereignty

among the States,” Shelby County v. Holder, 570 U.S.

529, 544 (2013) (quotation marks and emphasis

omitted), but also to infringe on the sovereignty of

foreign nations.

As James Madison explained in Federalist 42, one

of the reasons our Constitution was necessary is that

allowing States to engage in foreign-policy activities

threatened to “embroil the Confederacy with foreign

nations.” THE FEDERALIST NO. 42 (James Madison).

Thus, the Constitution allocated “the foreign relations

power to the National Government.” Am. Ins. Ass’n v.

Garamendi, 539 U.S. 396, 413 (2003); Zschernig, 389

U.S. at 432; Fuld, 606 U.S. at 15 (describing “the

Federal Government’s exclusive authority ‘[i]n

international relations and with respect to foreign

intercourse and trade’” (quoting Board of Trs. of Univ.

of Ill. v. United States, 289 U.S. 48, 59 (1933)). Given

this allocation of foreign-affairs authority, there is not

even a fig leaf of justification for states to apply their

own laws to activities taking place in foreign

countries. Cf. Movsesian v. Victoria Versicherung AG,

670 F.3d 1067, 1072 (9th Cir. 2012) (en banc). Boulder

seeks to use Colorado law to do precisely that, and the

results will predictably allow it to “embroil the

[United States] with foreign nations.” THE

FEDERALIST NO. 42 (James Madison); THE FEDERALIST

at NO. 44, at 299 (James Madison) (emphasizing “the

advantage of uniformity in all points which relate to

foreign powers”).

Petitioners are global companies, and Boulder

seeks to establish liability based on their global

activities. Exxon Mobil, for example, has an “active

exploration or production presence in about 35

21

countries” and operates “refining facilities in more

than 15 countries.” Progress Through Partnership at

4, EXXON MOBIL, https://perma.cc/5NDN-BR4Z. All of

these countries have important relationships with the

United States. Some share a border with the United

States and are our closest trading partners. Others

are a world away and are strategic military partners

in the fight against global terrorism. Some

countries—especially those in the Middle East that

heavily rely on fossil fuels to power their economies—

are not likely to welcome Boulder’s de facto tax on the

production of fossil fuels within their territory.

Applying Colorado law to directly attach liability to

drilling and refining operations in those countries

would increase the marginal cost of extracting and

refining their oil and thus harm their economies, in

addition to the dignitary harm to their sovereignty.

See Kurns v. R.R. Friction Prods. Corp., 565 U.S. 625,

637 (2012). Allowing 50 states to apply their own laws

to the extraction and refining of fossil fuels in the

Middle East would create a geopolitical nightmare,

undermining the United States’ ability to speak with

“one voice” when engaging in extremely sensitive

diplomatic endeavors. Japan Line, Ltd. v. County of

Los Angeles, 441 U.S. 434, 449 (1979).

Because the Senate is specifically tasked with

approving treaties with foreign nations, U.S. CONST.

art. II, § 2, cl. 2, amici are in a unique position to

appreciate the foreign-policy risks of Boulder’s novel

escapade. Senior members of the State Department

also agree that allowing state law to penalize actions

taking place in foreign countries would create a

foreign-relations nightmare. When Vermont and New

York attempted to legislatively extend their

regulatory powers across the globe, Deputy Secretary

22

of State Christopher Landau filed declarations that

laid out the dire foreign-policy consequences of their

actions. When faced with liability for actions on their

own soil, foreign nations “may seek to respond” by

“retaliating” in the form of increasing the costs on

U.S.-based fossil-fuel companies operating in their

countries. Decl. of Christopher Landau, Vermont,

supra, ECF No. 50-3 ¶ 18. If each state could extend

its powers into foreign nations, it would be “difficult—

if not impossible—to maintain a coherent national

position” on energy-policy issues. Id. ¶ 20.

The problems with Boulder’s lawsuit (and those

like it around the country) do not end there. Not only

does Boulder seek to use Colorado law to “embroil the

[United States] with foreign nations,” THE

FEDERALIST NO. 42 (James Madison), it also proposes

to have a jury of Coloradans decide how much money

Exxon and Suncor will owe for their actions in other

states and in foreign countries. Am. Compl. ¶ 544

(“Plaintiffs demand a trial by jury.”). Normally, juries

serve the public good because they are the “voice of the

community” in the judicial process. BMW of N. Am.,

517 U.S. at 600 (Scalia, J., dissenting); Barry v.

Edmunds, 116 U.S. 550, 565 (1886). That feature,

however, becomes a bug when the jury is seeking to

impose liability based on actions taken wholly within

a separate “community.” BMW of N. Am., 517 U.S. at

600 (Scalia, J., dissenting). A jury asked to decide the

amount of damages that will be imposed for conduct

taking place in other states and foreign countries

would have every incentive to rack up the bill, as the

benefits but not the costs will be felt by those in their

community.

23

II.

This Lawsuit Cannot Proceed as a

Regulation of Greenhouse-Gas Emissions.

The premise of Boulder’s complaint and the

Colorado Supreme Court’s decision—that this case is

about liability for the production, refining, sale, and

advertising of fossil fuels, see Pet.App.17a—makes

this an easy case under the extraterritorialregulations doctrine. But there is another way to

think about the theory of liability here: a regulation of

the emission of greenhouse gases. Those gases, after

all, are the manner in which Boulder allegedly suffers

its harm. As the Second Circuit concluded when facing

a similar lawsuit, “[a]rtful pleading cannot transform

the City’s complaint into anything other than a suit

over global greenhouse gas emissions. It is precisely

because fossil fuels emit greenhouse gases—which

collectively “exacerbate global warming”—that the

City is seeking damages” from producers of fossil

fuels. City of New York v. Chevron Corp., 993 F.3d 81,

91 (2d Cir. 2021); Minn. ex rel Ellison v. Am.

Petroleum Inst., 63 F.4th 703, 717–18 (8th Cir. 2023)

(Stras, J., concurring). Because the emission of

greenhouse gases is “a link in ‘the causal chain’” of the

Boulder’s damages, and because the Clean Air Act

preempts states from applying their own law to

establish liability based on out-of-state emissions,

these claims are preempted. City of New York, 993

F.3d at 91.

This Court has long held that states cannot apply

their own law in lawsuits that involve out-of-state airor water-pollution sources. Illinois v. City of

Milwaukee, 406 U.S. 91, 105 (1972) (Milwaukee

I); Int'l Paper Co. v. Ouellette, 479 U.S. 481, 488

(1987). Historically, disputes that involved air or

24

water moving from one state to another were

governed by the federal common law of interstate

pollution. Georgia v. Tenn. Copper Co., 206 U.S. 230,

237–38 (1907) (applying federal common law to a

dispute about “outside nuisances”). Indeed, an

“unbroken string of cases has applied federal law,” not

State law, to resolve such conflicts. City of New York,

993 F.3d at 91 (collecting cases). When transboundary

pollution is at issue, “federal interests . . . are

incompatible with the application of state law” for two

reasons. Id. Applying State law would (1) result in

emissions from a single source being regulated by up

to 50 State laws at a single moment, and (2) subvert

“basic interests of federalism” by allowing States

essentially to serve as judges in their own disputes.

Id. at 91–92 (quoting Milwaukee I, 406 U.S. at 105

n.6); AEP, 564 U.S. at 421.

Throughout our nation’s history, a dispute

involving interstate air pollution would have been

governed by the federal common law of interstate

pollution, as established by “known and settled

principles of national or municipal jurisprudence.”

Minn. ex rel Ellison, 63 F.4th at 718 (citation omitted)

(Stras, J., concurring) (cataloguing this history); see

Milwaukee I, 406 U.S. at 105; cf. THE FEDERALIST NO.

80 (Alexander Hamilton) (“Whatever practices may

have a tendency to disturb the harmony between the

States, are proper objects of federal superintendence

and control.”). The federal common law of interstate

water pollution and interstate air pollution, however,

have been displaced by the Clean Water Act and

Clean Air Act, respectively. City of Milwaukee v.

Illinois & Michigan,451 U.S. 304 (1981) (Milwaukee

II); AEP, 564 U.S. at 415. Thus, no plaintiff can bring

a claim under those sources of law. Id. at 429.

25

Much ink has been spilled by the lower federal

courts and state supreme courts about the exact

contours of the preemption analysis here. Some courts

have determined that the constitutional principles

that necessitated federal common law in the first

place continue to disable the use of state law, despite

federal common law being displaced as a rule of

decision in federal courts. See, e.g., City of New York,

993 F.3d at 92–93. Other courts have determined that

the sole question is the preemptive scope of the Clean

Air Act and that the reasons why federal common law

governed in the first place are irrelevant to the

inquiry. See e.g., City & Cnty. of Honolulu v. Sunoco

LP, 537 P.3d 1173, 1181 (Haw. 2023). The Colorado

Supreme Court took the latter position. Pet.App.11a.

Although the dispute over what happens to the

preemptive force of the federal common law when it is

displaced by a federal statute is interesting, that

debate is largely academic with respect to the Clean

Air Act. For even if the constitutional principles

undergirding the federal common law no longer allow

for the preemption state law, standard tools of

interpretation demonstrate that the Clean Air Act’s

preemptive scope reaches at least as far as the federal

common law’s preemptive scope. Thus, the assertions

of the Colorado and Hawaii Supreme Courts that

“‘displaced federal common law plays no part in this

court’s preemption analysis’” are wrong. Pet.App.11a

(quoting Honolulu, 537 P.3d at 1199). In other words,

a state law theory of liability that would have been

preempted under the federal common law would

likewise serve as an “obstacle” to the goals on the

Clean Air Act and thus be preempted. Hines v.

Davidowitz, 312 U.S. 52, 67 (1941); Geier v. Am.

Honda Motor Co., 529 U.S. 861, 881–82 (2000). And

26

because this suit would have been preempted under

the federal common law, it is preempted under the

Clean Air Act.

At least three tools of statutory interpretation

demonstrate that the Clean Air Act, at a minimum,

preempts any action that could not have proceeded

under the federal common law of interstate air

pollution.

First, consider the non-derogation canon.

“[S]tatutes will not be interpreted as changing the

common law unless they effect the change with

clarity.” ANTONIN SCALIA & BRYAN A. GARNER,

READING LAW: THE INTERPRETATION OF LEGAL TEXTS

318 (2012); Scharfield v. Richardson, 133 F.2d 340,

342 (D.C. Ct. App. 1942) (Vinson, J.). Thus when a

statute regulates an area traditionally occupied by the

common law, silence or gaps in the statute should not

be interpreted to abrogate well-settled common-law

rules. Id. If that statute enacts a rule that is obviously

inconsistent with the common law, the statute will

govern. But the fact that the statute alters the

common law in one way does not imply that it alters

the common law in another way. Id. The nonderogation canon has clear import in this context.

Before the Clean Air Act, the federal common law

provided the rule of decision and preempted states

from applying their own law to out-of-state pollution

sources. AEP, 564 U.S. at 423. The Clean Air Act

displaced the federal common law and appointed the

EPA as the “primary regulator of greenhouse[-]gas

emissions.” Id. at 428. It did not, however, purport to

alter the preemptive force of the federal common law

at all, let alone with clarity. Thus even if the federal

common law lost its preemptive force, the natural

27

implication is that the Clean Air Act simply

incorporated the same preemptive scope.

Second, consider the elephants-in-mouseholes

canon.5 Whitman v. Am. Trucking Ass’ns, 531 U.S.

457, 468 (2001). As the Colorado Supreme Court

understood things, the Clean Air Act’s displacement

of the federal common law of interstate air pollution

enacted a seismic shift in the governance of interstate

air pollution. From the beginning of our country’s

history, states could not apply their own law to out-ofstate emissions. See City of New York, 993 F.3d at 91

(collecting cases). But the Colorado Supreme Court

thinks that the Clean Air Act silently allowed

unprecedented state-law causes of action by creating

a comprehensive statutory scheme for the regulation

of such pollutants under federal law. It would be quite

strange, to say the least, for Congress to cede such

vast power to the states without a word.

Third, consider the negative-implication canon.

See Chevron U.S.A. Inc. v. Echazabal, 536 U.S. 73, 80

(2002). One of the Clean Air Act’s saving clauses

allows states “to adopt or enforce” a “standard or

limitation respecting emissions of air pollutants or . . .

a[] requirement respecting control or abatement of air

pollution” within its own borders that is stricter than

the one mandated by the EPA. 42 U.S.C. § 7416; see

Ouellette, 479 U.S. at 497 (interpreting the same

clause in the Clean Water Act). Allowing states to

impose more-stringent restrictions than the EPA

mandates on the release of air pollutants within their

This canon is often understood as the “major questions

doctrine” in the administrative-law context, but the fact that

Congress does not enact massive changes without notice applies

across the board.

5

28

own states leads to the negative implication that

states may not impose such restrictions on emitters in

other states. In other words, the negative implication

is that states are forbidden from doing precisely what

the federal common law forbade them from doing

before the enactment of the Clean Air Act. This

savings clause dovetails perfectly with the conclusion

that the Clean Air Act incorporated the preemptive

scope of the federal common law of interstate air

pollution.

Put together, these traditional canons of

interpretation point to a common-sense conclusion:

Congress did not sub silentio authorize a massive

expansion of state authority over interstate emissions

through the Clean Air Act.

Because this suit would have been preempted

before the passage of the Clean Air Act, it can only go

forward if the Clean Air Act authorizes it. Id. at 492.

The Clean Air Act does no such thing. Only two

provisions of the Clean Air Act could possibly be

relevant to authorizing this kind of suit, but neither

greenlights this kind of suit.

First is the “states’ rights” savings clause, which

establishes that “nothing in this chapter shall

preclude or deny the right of any State or political

subdivision thereof to adopt or enforce (1) any

standard or limitation respecting emissions of air

pollutants or (2) any requirement respecting control

or abatement of air pollution.” 42 U.S.C. § 7416. This

clause looks promising at first, but as described above,

this Court has interpreted the identical clause in the

Clean Water Act only to allow for the regulation of instate sources of pollution. Ouellette, 479 U.S. at 492.

Given that these clauses use the same wording and

29

are contained within similar statutes, they plainly

have the same meaning. City of New York, 993 F.3d at

99; Bell v. Cheswick Generating Station, 734 F.3d 188,

195–96 (3d Cir. 2013) (same).

The second potentially relevant clause is the

“citizen-suit savings clause,” which states that

“[n]othing in this section shall restrict any right which

any person (or class of persons) may have under any

statute or common law to seek enforcement of any

emission standard or limitation or to seek any other

relief.” 42 U.S.C. § 7604(e). Like the states’ rights

savings clause, however, the citizen-suit clause has

already been interpreted by this Court to allow for

suits under “the law of the [pollution’s] source [s]tate.”

Ouellette, 479 U.S. at 497. Thus, neither of the savings

clauses shows that the Clean Air Act has authorized

this lawsuit. Id.

III.

Conclusion

Boulder seeks to use Colorado law to impose its

policy preferences on the rest of the world. But

Colorado law does not govern activities in the other 49

states, much less countries thousands of miles away.

This Court should reverse.

30

Respectfully submitted,

CHARLES J. COOPER

Counsel of Record

ADAM P. LAXALT

BRADLEY L. LARSON

COOPER & KIRK, PLLC

1523 New Hampshire

Avenue, N.W.

Washington, D.C. 20036

(202) 220-9600

ccooper@cooperkirk.com

Counsel for Amici Curiae