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 PROFESSOR SAIKRISHNA B. PRAKASH

AS AMICUS CURIAE IN SUPPORT OF

PETITIONERS

_______________

JENNIFER K. HARDY

Counsel of Record

BOYDEN GRAY PLLC

800 Connecticut Ave NW,

Suite 900

Washington, DC 20006

(202) 955-0620

jhardy@boydengray.com

Counsel for Amicus Curiae

i

QUESTIONS PRESENTED

1. Whether federal law precludes state-law claims

seeking relief for injuries allegedly caused by the

effects of interstate and international greenhouse-gas

emissions on the global climate.

2. Whether this Court has statutory and Article

III jurisdiction to hear this case.

ii

TABLE OF CONTENTS

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

INTRODUCTION AND SUMMARY OF

ARGUMENT ....................................................... 2

ARGUMENT .............................................................. 7

I.

The Implications of Boulder’s Worldwide

Assertion of Legislative Authority Are Sobering

and Should Give This Court Pause. ................... 7

II.

The Constitution Bars Boulder’s Vagrant Theory

of Global Authority for Colorado. ..................... 12

A.

The Constitution Imposes Implied Limits on

States. ........................................................ 12

B.

Constitutional Structure Limits the

Extraterritorial Reach of State Authority. 15

C.

1.

At the Founding, a nation’s legislative

authority generally extended no further

than its own territory. ........................ 16

2.

By joining the Union, the States bound

themselves to a system that constrained

extraterritorial regulation. ................ 19

3.

Early Supreme Courts and executive

practice reflect the common view that

state legislative authority had

territorial limits. ................................ 23

The Founders Would Have Regarded This

Lawsuit as Fantastical. ............................. 25

III. National Pork Producers Reaffirmed Territorial

Limits on Sovereignty. ...................................... 28

CONCLUSION ......................................................... 31

iii

TABLE OF AUTHORITIES

PAGE(S)

CASES

The Apollon,

22 U.S. (9 Wheat.) 362 (1824) .............................. 23

Franchise Tax Bd. of Cal. v. Hyatt,

587 U.S. 230 (2019) .................................. 13, 16, 18

Georgia v. Tenn. Copper Co.,

206 U.S. 230 (1907) .............................................. 15

Kansas v. Colorado,

206 U.S. 46 (1907) .......................................... 14, 15

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

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

Learning Res., Inc. v. Trump,

146 S. Ct. 628 (2026) ............................................ 17

Louisiana v. Mississippi,

202 U.S. 1 (1906) .................................................. 14

McCulloch v. Maryland,

17 U.S. (4 Wheat.) 316 (1819) .......................... 5, 13

Nat’l Pork Producers Council v. Ross,

598 U.S. 356 (2023) ........................................ 28, 29

Ogden v. Saunders,

25 U.S. (12 Wheat.) 213 (1827) ............................ 14

Rose v. Himely,

8 U.S. (4 Cranch) 241 (1808) ............................... 23

iv

Shelby County v. Holder,

570 U.S. 529 (2013) .............................................. 14

Students for Fair Admissions, Inc. v.

President & Fellows of Harvard Coll.,

600 U.S. 181 (2023) .............................................. 11

U.S. Steel Corp. v. Multistate Tax Comm’n,

434 U.S. 452 (1978) .............................................. 16

U.S. Term Limits, Inc. v. Thornton,

514 U.S. 779 (1995) .............................................. 30

United States v. Bevans,

16 U.S. (3 Wheat.) 336 (1818) .............................. 23

Zivotofsky ex rel. Zivotofsky v. Kerry,

576 U.S. 1 (2015) .................................................. 14

CONSTITITIONAL PROVISIONS

U.S. Const. art. I, § 8 ................................................. 22

U.S. Const. art. I, § 10 ............................................... 22

U.S. Const. art. I, § 10, cl. 1 ................................ 12, 13

U.S. Const. art. I, § 10, cl. 3 ...................................... 23

INTERNATIONAL AGREEMENTS

Treaty of Alliance, Fr.-U.S.,

Feb. 6, 1778, 8 Stat. 6 .................................... 24, 25

Definitive Treaty of Peace, Gr. Brit.-U.S.,

Sept. 3, 1783, 8 Stat. 80 ................................. 24, 25

v

Consular Convention of 1788, Fr.-U.S.,

Nov. 14, 1788, 8 Stat. 106 .................................... 24

OTHER AUTHORITIES

The Antifederalist No. 11 (Agrippa)

(Morton Borden ed., 1965) ................................... 21

The Antifederalist No. 63 (The Federal Farmer)

(Morton Borden ed., 1965) ................................... 21

The Declaration of Independence (U.S. 1776) .... 26, 27

Emmerich de Vattel, The Law of Nations

(1797) .............................................................. 16, 17

EPA, Inventory of U.S. Greenhouse Gas

Emissions and Sinks: 1990–2022 (2024),

https://www.epa.gov/system/files/documents/

2024-04/us-ghg-inventory-2024-main-text_0418-2024.pdf ............................................................. 9

The Federalist No. 3 (John Jay) (Clinton

Rossiter ed., 1961) ................................................ 21

The Federalist No. 7 (Alexander Hamilton)

(Clinton Rossiter ed., 1961) ................................. 20

The Federalist No. 22 (Alexander Hamilton)

(Clinton Rossiter ed., 1961) ................................. 20

The Federalist No. 31 (Alexander Hamilton)

(Clinton Rossiter ed., 1961) ................................. 14

The Federalist No. 32 (Alexander Hamilton)

(Clinton Rossiter ed., 1961) ........................... 19, 20

vi

The Federalist No. 42 (James Madison)

(Clinton Rossiter ed., 1961) ........................... 19, 21

The Federalist No. 45 (James Madison)

(Clinton Rossiter ed., 1961) ................................. 19

The Federalist No. 80 (Alexander Hamilton)

(Clinton Rossiter ed., 1961) ....................... 6, 20–22

The Federalist No. 82 (Alexander Hamilton)

(Clinton Rossiter ed., 1961) ................................. 11

G.A. Res. 2625 (XXV), Declaration on Principles of

International Law Concerning Friendly

Relations and Cooperation Among States in

Accordance with the Charter of the United

Nations (Oct. 24, 1970) ........................................ 18

John Bassett Moore, A Digest of International

Law (1906) ............................................................ 17

Joseph Story, Commentaries on Conflict of Laws

(1834) .................................................................... 24

Joseph Story, Commentaries on the Constitution

of the United States (1833)....................... 13, 22, 25

Lassa Oppenheim, International Law: A Treatise

(1905) .............................................................. 16, 17

Letter from Thomas Jefferson to Edmond Charles

Genet (c. July 16, 1793), https://founders.

archives.gov/documents/Jefferson/01-26-020454 ...................................................................... 25

vii

Regulate, Merriam-Webster Dictionary, https://

www.merriam-webster.com/dictionary/

regulate (last visited May 19, 2026) .................... 11

Resolutions of the Stamp Act Congress, Resol. V

(Oct. 19, 1765), in Documents of American

History 57 (7th ed. 1963) ..................................... 25

Restatement (Fourth) of Foreign Relations Law

(A.L.I. 2018).......................................................... 18

Samuel Johnson, A Dictionary of the English

Language (4th ed. 1773), https://johnsons

dictionaryonline.com/1773page/regress .............. 11

St. George Tucker, Blackstone’s Commentaries

(1803) .................................................................... 22

Thomas Rutherforth, Institutes of Natural Law

(1756) .................................................................... 17

Virginia Stamp Act Resolutions (May 30, 1765),

in Documents of American History 55

(7th ed. 1963)........................................................ 25

1

INTEREST OF AMICUS CURIAE 1

Professor Saikrishna B. Prakash is the James

Monroe Distinguished Professor of Law and the

Horace W. Goldsmith Research Professor of Law at

the University of Virginia Law School, where he has

taught constitutional law, foreign relations law, and

presidential powers. He has authored over 80 law

review articles and a handful of books. Professor

Prakash seeks to help the Court better understand

the Constitution’s original meaning as it decides vital

legal questions.

1 No party’s counsel authored this brief in whole or in part. No

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

monetary contribution intended to fund its preparation or

submission.

2

INTRODUCTION AND SUMMARY OF

ARGUMENT

Boulder’s theory of Colorado’s legislative reach is

a tad broad. In this case, Boulder argues that

Colorado, one of 50 States in the Union, enjoys

continental legislative power. Boulder supposes that

Colorado may regulate fossil fuel production

throughout the United States, because Boulder

believes that such production has a distant but

deleterious effect within Colorado. Boulder reasons

that in a nation with far less production of fossil fuels,

there would be far fewer greenhouse gas emissions.

Yet if it is the emission of greenhouse gases that

harms Boulder, and if Boulder can sue fossil fuel

producers—entities with little or no emissions of their

own—Boulder must suppose that Colorado can

regulate, nationwide, all entities that burn fossil

fuels, including utilities, factories, and trucking firms,

as well as those that emit greenhouse gases without

any combustion, like crop and dairy farmers. Colorado

might even regulate America’s homeowners, millions

of whom burn greenhouse gases when they cook their

food and heat their homes. More so than fossil fuel

producers, these sources are responsible for the

release of greenhouse gases into the atmosphere.

Furthermore, if Colorado can regulate energy

producers upstream of actual emitters, why not

regulate downstream as well? That is, Boulder may

imagine that Colorado could, if it so chose, regulate

nationwide purchases of greenhouse gas-intensive

products and services, including concrete, steel,

livestock, fertilizers, plastics, textiles, and chemicals.

After all, if there was less demand for these products,

3

there would be far fewer emissions. Under this

approach, Colorado might impose liability, across the

nation, on road builders, home constructors, and even

ordinary consumers. This may seem beyond the pale,

even fanciful. But the same could be said of Boulder’s

attempt to seek damages for the nationwide

production of fossil fuels.

Boulder’s claim to regulate does not end at the

water’s edge. Boulder asserts that Colorado enjoys

legislative authority that encircles the globe, in a

fashion that would make Imperial Rome and the

British Empire blush. Boulder’s suit is predicated on

its view that Colorado has the legislative power to

regulate producers and emitters worldwide because

each one, large and small, contributes to greenhouse

gas emissions. Indeed, the producers and emitters

outside the United States are responsible for the bulk

of emissions. The rice farmer in India, the cook in

Peru, and the coal company in South Africa—each of

them emits greenhouse gases and could be in

Boulder’s bullseye.

To be sure, Boulder has not yet sued greenhouse

gas emitters either nationwide or worldwide. Nor has

it sought to regulate consumers of greenhouse gasintensive products. Yet its lawsuit reflects a desire to

change the world and rests on a long-arm theory of

regulatory power, where Colorado may regulate

worldwide to stem the effects of greenhouse gas

emissions. Its current forbearance is hardly a

concession that it cannot regulate emissions and

consumption across the globe.

Now, Boulder may be unable (or unwilling) to sue

all those it might wish to reach. Neither Colorado’s

4

courts nor the federal courts may have jurisdiction to

try every producer of greenhouse gases. But whether

American courts can exercise personal jurisdiction

over every producer of fossil fuels, Boulder (population

of approximately 106,000) effectively claims for

Colorado legislative authority over 8 billion people,

for everyone emits greenhouse gases and everyone

consumes greenhouse gas-intensive products. We

should not conflate the undoubted limits of judicial

jurisdiction with the indisputable breadth of Boulder’s

theory of Colorado’s regulatory power. If a Chilean

visits Colorado—and she emits greenhouse gases back

home because she drives a car or has a cow, or both—

Boulder must suppose that Colorado has the

legislative power to seek damages from her and

judicial power to find her liable for emissions in

Santiago, Chile.

Boulder appears unaware or indifferent to the

implications for itself and the United States. If

Boulder, Colorado, may sue producers around the

nation and the world, other sovereigns will retaliate.

To begin with, Boulder City, Nevada, could sue

producers and emitters throughout the United States,

including those in Boulder, Colorado. No one should

doubt that other States, and subunits, would sue for

actions beyond their borders. The ensuing

recriminations and conflicts would not only be

disheartening, they would threaten our Federalism.

Further, the German city of Stein might regulate

production and emissions within America. That is,

once American sovereigns start imperiously

regulating actions in foreign nations, those nations

will claim long-arm regulatory authority over what

5

transpires in America. Boulder’s theory of

transnational legislative power envisions hundreds of

sovereigns regulating activities across the entire

globe, deep into the interior of every nation.

Boulder would have this Court endorse a theory

that would upend a world of sovereign, independent

nation-states and replace it with a disordered scheme

in which no country has exclusive sovereignty, let

alone any measure of true independence. Some

nations might compel firms to extract fuels, while

others might attach draconian liability for the same

mining or drilling. Some nations might believe that

the burning of fossil fuels helps raise their people’s

standard of living and incentivize their consumption

through subsidized prices; others might scowl at this

encouragement and sue the person who uses fossil

fuels to run her factory or to heat her home. This

regulatory cacophony is not a bug in Boulder’s theory;

it seems to be a feature.

There is a sound and ancient answer to Boulder’s

misreading of Colorado’s legislative power. Long ago,

in McCulloch v. Maryland, 17 U.S. (4 Wheat.) 316,

430–32 (1819), Chief Justice John Marshall rightly

said the parts cannot control the whole. He meant

that a single State could not tax an instrumentality of

the whole nation, even when that entity operated

within that State. But in an extravagance that

Maryland perhaps never imagined, Boulder claims on

behalf of Colorado not only the legislative power to

regulate within every State in the Union, but also

across the whole world. In doing so, Boulder claims

such legislative power for every sovereign, domestic

6

and foreign, for if Boulder is right all of them may

extend their laws and policies across the globe.

The Constitution bars Boulder’s vagrant claims

of legislative and regulatory authority. Like other

sovereigns, Colorado’s sovereignty is territorial,

essentially confined to Colorado. In the eighteenth

century, nation-states had territorial jurisdiction and

lacked legislative power to regulate foreigners in

foreign lands. By ratifying the Constitution and

joining the Union, the thirteen original States and

their 37 later admittees effectively yielded up the

right to even attempt to regulate such conduct.

If anyone in the United States can unilaterally

regulate the conduct of foreigners in foreign states, it

would be Congress, through the delicate and careful

exercise of its legislative powers. This Court should be

deeply reluctant to conclude that “the peace of the

WHOLE [was] left at the disposal of a PART.” The

Federalist No. 80, at 476 (Alexander Hamilton)

(Clinton Rossiter ed., 1961). If, however, Boulder is

right, every State (and many localities) has legislative

power to enflame each other and every nation under

heaven. And every other nation has the lawful power

to regulate production and emission in the United

States.

A part of this Union cannot control what occurs

in the other parts. A part of this Union cannot

graspingly reach across national borders to regulate

what occurs in other nations and thereby antagonize

those sovereigns. And a part of this Union should not

insist upon extranational regulatory power in a

7

manner that invites reciprocal regulation from more

than a hundred foreign sovereigns.

Boulder’s theory of Colorado’s regulatory reach

well exceeds the latter’s constitutional grasp. This

Court should reject Boulder’s novel reading of

Colorado’s legislative jurisdiction, one grounded on a

misunderstanding of territorial sovereignty, our

federal system, and the international order.

ARGUMENT

I.

The Implications of Boulder’s Worldwide

Assertion of Legislative Authority Are

Sobering and Should Give This Court

Pause.

Boulder’s theory of liability implies that Colorado

can regulate any activity—domestic or foreign—no

matter how remote or tenuous the effect is within the

State. Per Boulder, worldwide greenhouse gas

emissions trigger climate change that injures

Boulder. Yet Boulder has not sued emitters; it has

sued fossil fuel producers. This is telling.

If Boulder can sue fossil fuel producers for the

harm arising from the subsequent use of those fuels,

then it clearly can sue greenhouse gas emitters. The

latter actually send greenhouse gases into the

atmosphere, either through burning fossil fuels or

engaging in activities (spreading fertilizer or dairy

farming) that emit greenhouse gases. Hence Boulder

must suppose that it could seek damages from any

domestic user of fossil fuels, from manufacturers to

shippers to car drivers. More so than producers,

8

emitters of greenhouse gases are the ones, under

Boulder’s theory, that cause it harm.

The authority Boulder claims for Colorado may

extend further. If Boulder can regulate the producers

of fossil fuels, who are not the major emitters, then,

perhaps it may regulate consumers of greenhouse-gasintensive products and services. After all, if people

limited their purchase of greenhouse-gas-intensive

products, many emitters (factories, shippers, dairy

farmers, etc.) would emit far less. No one doubts that

end-user consumption is a major driver of emissions.

To be sure, Boulder never expressly claims that

Colorado can regulate consumption of greenhouse-gas

intensive products. Yet such authority seems to follow

from its theory. If Colorado can attach liability for

distant acts because they affect Colorado, then

Colorado essentially claims the legislative power to

regulate those distant acts in other ways. Put another

way, whether the liability that Colorado attaches

arises from the common law of Colorado or a Colorado

statute does not matter. Further, no sensible theory of

sovereignty would sanction Colorado’s attempt to

attach

tort

liability

extraterritorially

while

simultaneously barring the extraterritorial regulation

of the consumption of fossil fuel-intensive products.

To better assess the reach of Boulder’s long-arm

theory of Colorado’s regulatory authority, consider the

people and firms that Colorado could regulate. Under

Boulder’s theory, Colorado could regulate, and collect

damages from, oil, natural gas, and coal firms across

the United States. Additionally, Colorado could

regulate, across the nation, all emitters, including

factories, utilities, and farmers (farms are significant

9

emitters). Colorado could also regulate, and recoup

damages from, homeowners (users of wood, gas, or

oil), for American homes emit greenhouse gases.

Finally, Colorado could regulate purchases of

greenhouse gas-intensive products. It could limit the

nationwide consumption of dairy products, concrete,

steel, aluminum, livestock, fertilizers, plastics,

textiles, chemicals, and electricity. 2 Concrete and

steel are used in homes, apartments, bridges, and

skyscrapers. Grocery stores buy milk, cheese, and

other dairy products. Farmers buy fertilizer to grow

crops that people and livestock eat. Hospitals

purchase surgical masks and other single-use items

for patients and staff. Boulder’s theory contemplates

that it can regulate them all, for if there were no

demand for these products, emissions would be lower.

In short, Boulder imagines it can regulate actions

nationwide that adversely affect Boulder. Hence it can

regulate and sue fossil fuel producers, greenhouse gas

emitters, and consumers of fossil-fuel intensive

products. No one doubts that each contributes,

directly or indirectly, to greenhouse gas emissions.

The regulatory authority Boulder asserts does

not stop at the shores of the United States; it circles

the globe. Boulder’s suit is premised on worldwide

emissions causing a worldwide effect that allegedly

impacts Boulder. This theory seems to subject every

person—over 8 billion—and countless entities

2 See generally EPA, Inventory of U.S. Greenhouse Gas Emissions

and Sinks: 1990–2022 (2024), https://www.epa.gov/system/files/

documents/2024-04/us-ghg-inventory-2024-main-text_04-182024.pdf.

10

worldwide to Colorado’s legislative authority.

Whether someone is a cattle rancher in Argentina, a

taxi owner in Singapore, or a cook in Zimbabwe, each

would be subject to Colorado’s rules. After all, each

contributes to fossil fuel emissions.

Boulder’s theory of worldwide legislative power

for Colorado opens a Pandora’s Box. If Colorado can

regulate emissions worldwide, as Boulder claims,

then every other sovereign can do the same. For our

purposes, that would mean every other State of the

Union and every foreign nation, and each of its

sovereign subunits, can regulate fossil fuel producers

and greenhouse gas emitters in the United States.

Boulder, Idaho, could regulate energy producers in

Boulder, Colorado. Further, the Republic of Greece,

which currently has no control over American soil,

could attach liability for emissions from Athens,

Georgia. And the Russian Federation, hardly a

shrinking violet, could impose liability on

homeowners in Moscow, Idaho.

We must bear in mind that the United States

remains one of the top producers of fossil fuels and one

the biggest emitters of greenhouse gases. In the face

of Boulder’s lawsuit, and the hundreds of others that

would follow in its wake, why would Japan or

Indonesia refrain from imposing liability on U.S.

farmers or U.S. fossil fuel producers for contributing

to greenhouse gases? U.S. corporations and citizens

could not easily escape liability. Japan, Indonesia, and

the rest of the world could come to the United States

and file lawsuits, invoking a theory of climate liability

under their own laws, against corporations or

individuals over which a U.S. court had jurisdiction.

As Alexander Hamilton rightfully observed, the laws

11

of “Japan, not less than of New York, may furnish the

objects of legal discussion to our courts.” The

Federalist No. 82, at 493.

It matters not a whit that Boulder asserts

Colorado’s supposed authority through tort liability

rather than via constraining production or emissions.

First, “‘what cannot be done directly cannot be done

indirectly,” because “[t]he Constitution deals with

substance, not shadows,’ and the prohibition … is

‘levelled at the thing, not the name.’” Students for Fair

Admissions, Inc. v. President & Fellows of Harvard

Coll., 600 U.S. 181, 230 (2023) (alteration omitted)

(quoting Cummings v. Missouri, 71 U.S. (4 Wall.) 277,

325 (1866)).

Second, and more importantly, liability drives

behavior no less than other more obvious directives.

This Court has recognized that liability is a form of

regulation. See, e.g., Kurns v. R.R. Friction Prods.

Corp., 565 U.S. 625, 637 (2012) (“[R]egulation can be

effectively exerted through an award of damages, and

the obligation to pay compensation can be, indeed is

designed to be, a potent method of governing conduct

and controlling policy.” (cleaned up)). The Court was

right, for tort liability seeks to “regulate,” namely

“adjust by rule or method” the underlying behavior. 2

Samuel Johnson, A Dictionary of the English

Language (4th ed. 1773), https://johnsonsdictionary

online.com/1773page/regress; Regulate, MerriamWebster Dictionary, https://www.merriam-webster.

com/dictionary/regulate (last visited May 19, 2026)

(“to govern or direct according to rule”).

Boulder seeks to override the structural principle

from McCulloch, one immanent in the Constitution.

12

Boulder’s theory has a part of the Union controlling

actions throughout the whole nation. Not content with

that reach, Boulder thinks Colorado can regulate the

entire world. Were Boulder to prevail, no one should

doubt that the rest of the nation and world would

respond in kind. Such a brash assertion of worldwide

legislative authority by a small section of a single

nation is incongruous.

II.

The Constitution Bars Boulder’s Vagrant

Theory of Global Authority for Colorado.

The Constitution imposes limits on state

authority. Some are express. Some are implied.

Indeed, the Court has recognized several implied

structural limits on States. One of these is especially

relevant here: state legislative authority is generally

limited to its territory. The Founders were well aware

of this constraint, for they had just fought a war to

vindicate America’s territorial sovereignty. After

independence, no one else could regulate American

soil. Nor could one State of the Union regulate any

other State, for each was free and independent.

Boulder’s attempt to deploy state tort law to regulate

the entire United States and the world would have left

the Founders thunderstruck.

A. The Constitution Imposes Implied Limits

on States.

Article I, section 10 imposes many express limits

on state authority. Among other things, they cannot

coin money, or pass bills of attainder, ex post facto

laws, or laws impairing contractual obligations. U.S.

Const. art. I, § 10, cl. 1.

13

Yet section 10 is hardly an exhaustive list of the

limits on States. To read it that way is to embrace the

“ahistorical literalism” that this Court has rightly

rejected. Franchise Tax Bd. of Cal. v. Hyatt, 587 U.S.

230, 247 (2019). Instead, “there are implied, as well as

express, prohibitions in the constitution upon the

power of the states.” 3 Joseph Story, Commentaries on

the Constitution of the United States 274 (1833).

Failing to enforce these implied limits permits States

to unilaterally unravel the Constitution that We the

People ordained and established.

The Court drew on implied structural limits in

McCulloch. It found that “the unavoidable

consequence of that supremacy which the constitution

has declared” is that “states have no power, by

taxation or otherwise, to retard, impede, burden, or in

any manner control, the operations of the

constitutional laws enacted by congress to carry into

execution the powers vested in the general

government.” 17 U.S. at 436.

Sovereign immunity is another example of an

implied limit. Though not explicit in the Constitution,

“at the time of the founding, it was well settled that

States were immune under both the common law and

the law of nations,” and “the Constitution’s use of the

term ‘States’ reflects both of these kinds of traditional

immunity.” Hyatt, 587 U.S. at 241.

The Constitution likewise implicitly constrains

state authority in foreign affairs. Although some of

these limits are explicit, see U.S. Const. art. I, § 10, cl.

1 (prohibiting the making of treaties or alliances),

others are implied. The President alone may recognize

nations, governments, and diplomats. Congress and

14

the States may not. See Zivotofsky ex rel. Zivotofsky v.

Kerry, 576 U.S. 1, 21 (2015).

The principle of equal state sovereignty also

restrains the States. “[O]ur Nation ‘was and is a union

of States, equal in power, dignity and authority.’”

Shelby County v. Holder, 570 U.S. 529, 544 (2013)

(quoting Coyle v. Smith, 221 U.S. 559, 567 (1911)).

This long-standing principle means that “[e]ach 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.” Kansas v.

Colorado, 206 U.S. 46, 97 (1907). Where “the extent

and the limitations of the rights of the two states”

collide, this Court should “settle that dispute in such

a way as will recognize the equal rights of both and at

the same time establish justice between them.” Id. at

98; see Ogden v. Saunders, 25 U.S. (12 Wheat.) 213,

369 (1827) (“But when … the States pass beyond their

own limits … there arises a conflict of sovereign

power, … which renders the exercise of such a power

incompatible with the rights of other States, and with

the constitution of the United States.”).

Equal sovereignty has influenced how this Court

has addressed various interstate conflicts. Because

States cannot impose their own rules on one another,

this Court has settled interstate boundary disputes,

not by reference to state law but to federal common

law. See, e.g., Louisiana v. Mississippi, 202 U.S. 1, 50–

53 (1906) (resolving boundary dispute between

Louisiana and Mississippi using federal common law).

Particularly relevant to this case, the principle of

equal state sovereignty has also led the Court to adopt

a federal rule to settle disputes over water rights, see

15

Kansas, 206 U.S. at 97–98, and pollution, see Georgia

v. Tenn. Copper Co., 206 U.S. 230, 237 (1907) (when

faced with an interstate nuisance, the proper

“alternative to force is a suit in this court”).

Many of these limits lack a firm grounding in the

text. Yet they all reflect the nature of sovereignty and

the Constitution’s structure, including the partial

subordination of the States to the national

government and each State’s limited jurisdiction.

B. Constitutional Structure Limits the

Extraterritorial Reach of State Authority.

Another implied limit on state sovereignty, one

recognized by the Founders and early legal

commentators, inheres in the tight link between

territory and sovereignty. No State may regulate

activity in another merely because it causes some

effects at home. Maryland cannot regulate gun sales

and possession in Virginia because some persons will

transport them across the Potomac. New York cannot

regulate violence in New Jersey because some of it will

spill over to the Empire State. California cannot

regulate Nevada’s gaming industry even though

millions of Californians gamble there. As should be

obvious, the Constitution never declares or implies

that by joining the Union, Virginia granted New York

authority to regulate within Virginia.

These limits reflect sensible understandings of

the relationship between territory and sovereignty

and the preconditions for the harmonious relations

amongst co-equal sovereigns. Indeed, absent

territorial limits on a State’s legislative power, no

State in the Union could be sovereign in any real sense

16

because every State would regulate everywhere across

the nation, effectively erasing state boundaries. State

sovereignty rests on limited federal power and the

absence of other sovereigns, be it Indiana or India,

exercising concurrent territorial authority. The

Founders

recognized

these

principles

and

incorporated them into the Constitution’s design.

1. At the Founding, a nation’s legislative

authority generally extended no further

than its own territory.

Leading international law treatises articulated

the territorial limits of sovereignty. Emmerich de

Vattel was “the founding era’s foremost expert on the

law of nations.” Hyatt, 587 U.S. at 239. 3 In his

influential The Law of Nations, Vattel observed: “The

whole space over which a nation extends its

government, becomes the seat of its jurisdiction, and

is called its territory.” Emmerich de Vattel, The Law

of Nations 99 (1797). Further, “[i]t is her province …

to exercise justice in all the places under her

jurisdiction.” Id. at 166; see also 1 Lassa Oppenheim,

International Law: A Treatise 171 (1905)

(“sovereignty is territorial supremacy”).

Intruding on another sovereign’s territory was a

cause of war, underscoring the link between territory

and sovereignty. Vattel said that “[t]he least

encroachment on the territory of another is an act of

injustice.” Vattel, supra, at 169. For that reason,

3 Vattel was the “most widely cited [international jurist] in the

first 50 years after the Revolution.” U.S. Steel Corp. v. Multistate

Tax Comm’n, 434 U.S. 452, 462 n.12 (1978) (citing 1 James Kent,

Commentaries on American Law 18 (1826)).

17

Vattel cautions that “to avoid the commission of any

such act, and to prevent every subject of discord … the

limits of territories ought to be marked out with

clearness and precision.” Id.; see also Oppenheim,

supra, at 173 (due to “territorial supremacy … a State

is not allowed to send its troops … or to exercise an

act of administration or jurisdiction on foreign

territory, without permission”).

Sovereigns were equals, with no nation having

inherent authority over the territory of another.

Thomas Rutherforth in his Institutes of Natural

Law—another “treatise routinely cited by the

Founders,” Learning Res., Inc. v. Trump, 146 S. Ct.

628, 684–85 (2026) (Thomas, J., dissenting)—

declared: “Every state has, by the law of nations, an

exclusive jurisdiction over its own territory.” 2 Thomas

Rutherforth, Institutes of Natural Law 593 (1756)

(emphasis added). Per Rutherforth, a nation “could

not be a distinct … body, if its members were subject

to any other jurisdiction besides its own.” Id. at 517;

see id. (each nation “has the right to judge for itself,

how far its own members are to be punished, and

whether they are to be punished at all”). Because each

nation had exclusive territorial jurisdiction, “no one …

ha[d] jurisdiction over the rest.” Id. at 595.

Because a nation’s legislative authority generally

ended at its borders, diplomacy and treaties were

utilized to address troubling conduct in other nations.

As Vattel explained, “Between bodies politic,—

between sovereigns who acknowledge no superior on

earth,—treaties are the only means of adjusting their

various pretensions,—of establishing fixed rules of

conduct.” Vattel, supra, at 229; see also 1 John Bassett

18

Moore, A Digest of International Law 466–67 (1906)

(“As each nation’s sphere of action is circumscribed by

jurisdictional limits … there are interests common to

all for the preservation of which international

cooperation is essential. Such cooperation is secured

by international agreements[.]”). 4

After the Declaration of Independence and under

the Articles of Confederation, the “Free and

Independent States” operated under these familiar

limits on sovereignty. See Hyatt, 587 U.S. at 237–38

(cleaned up). Per international law, “independence

‘entitled’ the [States] ‘to all the rights and powers of

sovereign states.’” Id. at 237–38 (quoting McIlvaine v.

Coxe’s Lessee, 8 U.S. (4 Cranch) 209, 212 (1808)). Of

course, no free and independent nation claimed the

authority to regulate extraterritorially. France did not

regulate actions in England; Japan did not regulate

4 Modern customary international law suggests a more expansive

prescriptive (legislative) jurisdiction for nations, extending it

beyond territory to effects, nationality, passive personality, the

protective principle, and universal jurisdiction. Restatement

(Fourth) of Foreign Relations Law § 402 (A.L.I. 2018).

Nonetheless, nations are not to exercise this authority where it

would be “unreasonable.” Id. § 405. They also must respect each

other’s equal sovereignty. See, e.g., G.A. Res. 2625 (XXV),

Declaration on Principles of International Law Concerning

Friendly Relations and Cooperation Among States in Accordance

with the Charter of the United Nations (Oct. 24, 1970).

The federal government is the entity within the United States

that can properly (and judiciously) exercise America’s greater

rights to legislative jurisdiction. If the President (with Senate

consent) made a fossil fuels treaty, one that regulated producers

worldwide, that would pose different questions. Likewise, were

Congress to impose liability on global producers and emitters,

that too would be far removed from a State’s unilateral attempt

to assert long-arm regulatory power.

19

actions in Russia. Had either France or Japan made

such a move, it would have given cause for war.

2. By joining the Union, the States bound

themselves to a system that constrained

extraterritorial regulation.

The Constitution rests on this recognition of the

territorial reach of legislative power. In Federalist No.

32, Alexander Hamilton observed that “the State

governments would clearly retain all the rights of

sovereignty which they before had, and which were

not, by [the Constitution], exclusively delegated to the

United States.” The Federalist No. 32, at 198.

That preexisting sovereignty was generally

limited to state territory. As James Madison

elsewhere explained, “[t]he powers reserved to the

several States will extend to … the internal order,

improvement, and prosperity of the State.” The

Federalist No. 45, at 292–93 (emphasis added).

Madison knew of these territorial limits on state

power. For example, he saw the need for a uniform

federal bankruptcy law. Such a law, he observed,

would “prevent so many frauds where the parties or

their property may lie or be removed into different

States.” The Federalist No. 42, at 271. His cogent

point presupposed difficulties arising from the

territorial limits on each State’s reach. The

Constitution supplied federal solutions to this and

other interstate problems. It surely did not implicitly

grant each State a power to regulate beyond its

borders, one that no sovereign in that era enjoyed.

To the contrary, the Constitution “divested” some

state legislative power “in favor of the Union.”

20

Federalist No. 32, at 201 (Alexander Hamilton). The

Founders curbed state power because of their

experiences under the Articles of Confederation. The

Federalist Papers discuss the discord that arises

when States prioritize their own policies at the

expense of the whole, a tendency that would poison

interstate and international relations. Interstate

conflicts ranged from territorial disputes to

burdensome state regulations on interstate commerce

to disagreements over the public debt. The Federalist

No. 7 (Alexander Hamilton), at 60–64.

Conflict among the States had caused bitter

feelings. Hamilton described how “[t]he interfering

and unneighborly regulations of some States … have,

in different instances, given just cause of umbrage

and complaint to others.” The Federalist No. 22, at

144. And “if not restrained by a national control,”

Hamilton worried they “would be multiplied and

extended till they became not less serious sources of

animosity and discord than injurious impediments to

the intercourse between the different parts of the

Confederacy.” Id. at 144–45. Without the Union, he

argued “we may reasonably expect from the gradual

conflicts of State regulations, that the citizens of each

would at length come to be considered and treated by

the others in no better light than that of foreigners

and aliens.” Id. at 145. In his view, “[w]hatever

practices may have a tendency to disturb the harmony

between the States, are proper objects of federal

superintendence and control.” The Federalist No. 80,

at 477–78.

The proclivity of States to pursue their narrow

interests also jeopardized relations with other

nations. The Articles of Confederation, unlike the

21

proposed Constitution, did not provide authority to

define and punish offenses against the law of nations,

meaning it was, in Madison’s view, left “in the power

of any indiscreet member to embroil the Confederacy

with foreign nations.” The Federalist No. 42, at 265.

Hamilton raised similar concerns: “the peace of

the WHOLE ought not to be left at the disposal of a

PART. The Union will undoubtedly be answerable to

foreign powers for the conduct of its members.” The

Federalist No. 80, at 476. John Jay, the former

Secretary of Foreign Affairs, observed that treaty

violations by the States might lead to war. The

Federalist No. 3, at 43–44. If the Founders believed

that little Rhode Island could somehow regulate

British Canada and Spanish Florida, something sure

to raise overseas hackles, they would have expressly

restrained the States. They did not do so because they

could not imagine a State extending its legislative

reach across the Union and around the globe.

Even the Anti-Federalists, the votaries of state

authority, did not suppose that States could claim

authority over the entire nation, let alone the world.

Agrippa wrote that under the Articles of

Confederation, each State “has within its own limits

the sovereignty over its citizens, while some of the

general concerns are committed to Congress.” The

Antifederalist No. 11, at 28 (Morton Borden ed., 1965)

(emphasis added). Similarly, The Federal Farmer

wrote: “The states being sovereign and independent,

are all considered equal.” The Antifederalist No. 63,

at 183. That independence meant territorial

sovereignty. Massachusetts could neither regulate

Connecticut nor China. Nothing in these statements

22

hints at the abnormal scheme that Boulder imagines,

with freewheeling States imposing tort liability

worldwide and foreign nations doing the same on

every person in the United States.

With the Constitution’s creation of the Union,

any power to regulate across state lines rests with

Congress. See U.S. Const. art. I, § 8; The Federalist

No. 80, at 477–78 (Alexander Hamilton) (“Whatever

practices may have tendency to disturb the harmony

between the States, are proper objects of federal

superintendence and control.”). The Constitution

presupposed that “the municipal laws of no one state

can be resorted to as a general rule for the rest.” 1 St.

George Tucker, Blackstone’s Commentaries, App.

Note D, at 152 (1803) (emphasis added).

Similarly, any ability to unilaterally address

matters outside the United States would rest with

Congress, and not the individual States, or their

thousands of subunits. U.S. Const. art. I, §§ 8, 10. As

Justice Joseph Story wrote, “it is clear, that no state

[of the Union] can introduce any system, which shall

extend beyond its own territorial limits, and the

persons, who are subject to its jurisdiction.” 3 Story,

Commentaries on the Constitution, supra, at 7; see also

1 Tucker, supra, App. Note D, at 151 (“[T]he

municipal law of one state or nation has no force or

obligation in any other nation.”).

The Framers recognized that States might have

issues with neighbors, domestic and foreign, and left

open a narrow and clear path by which they might

regulate beyond their borders: interstate compacts.

Compacts with Utah and Mexico might grant

Colorado regulatory power over each. However,

23

Colorado would need the consent of Utah, Mexico, and

Congress, for compacts are sovereign contracts and all

state compacts require the consent of Congress. U.S.

Const. art. I, § 10, cl. 3. Crucially, Congress may judge

whether Colorado’s proposed compacts would serve

the interest of the Union. Yet, Boulder’s theory that

Colorado can regulate any extraterritorial activity

that remotely affects it would render the Compact

Clause largely irrelevant, for each State of the Union

would enjoy inherent unilateral authority to regulate

beyond its borders. The Compact Clause (and the

Treaty Clause) reflects sound and inherent limits on

a sovereign’s legislative power. Colorado cannot

escape those constraints by unilaterally imposing tort

liability nationwide and globally.

3. Early Supreme Courts and executive

practice reflect the common view that state

legislative authority had territorial limits.

In 1808, Chief Justice Marshall, writing in a

capture case, declared: “It is conceded that the

legislation of every country is territorial; that beyond

its own territory, it can only affect its own subjects or

citizens.” Rose v. Himely, 8 U.S. (4 Cranch) 241, 279

(1808). Territory was a critical limit: “[T]he pacific

rights of sovereignty must be exercised within the

territory of the sovereign.” Id.

In the decades that followed, the Court continued

to reaffirm this principle. See, e.g., United States v.

Bevans, 16 U.S. (3 Wheat.) 336, 386–87 (1818) (“the

jurisdiction of a state is co-extensive with its territory;

co-extensive with its legislative power”); The Apollon,

22 U.S. (9 Wheat.) 362, 370 (1824) (“The laws of no

nation can justly extend beyond its own territories,

24

except so far as regards its own citizens. They can

have no force to control the sovereignty or rights of

any other nation, within its own jurisdiction.”).

As Justice Story explained in Commentaries on

the Conflict of Laws: “That the laws … of any state

cannot by any inherent authority be entitled to

respect extra-territorially, or beyond the jurisdiction

of the state, which enacts them, is the necessary result

of the independence of distinct sovereignties.” Joseph

Story, Commentaries on Conflict of Laws 22 (1834)

(quoting Blanchard v. Russell, 13 Mass. 1, 4 (1816)).

Early executive practice likewise demonstrates

the link between sovereignty and territory. The 1783

Treaty of Paris, concluding the Revolutionary War,

saw Great Britain relinquish all her claims to the

“government, propriety and territorial rights” over the

United States. Definitive Treaty of Peace, Gr. Brit.U.S., art. 1, Sept. 3, 1783, 8 Stat. 80, 81. This British

renunciation served as recognition of America’s

territorial sovereignty. Similarly, our first treaty with

France saw the latter guarantee the “sovereignty and

independence, absolute and unlimited” of the United

States. Treaty of Alliance, Fr.-U.S., art. XI, Feb. 6,

1778, 8 Stat. 6, 10. The guarantee would have been

hollow had France supposed that it could regulate acts

within the United States.

As noted earlier, an international agreement

could create an exception to a nation’s exclusive

authority over a sovereign territory. The 1788

Consular Convention between the United States and

France created several exceptions, granting both

countries authority to take testimony and decide

certain legal matters within each other’s territory.

25

Fr.-U.S., Nov. 14, 1788, 8 Stat. 106. Yet when France

established capture courts within the United States,

the Secretary of State rejected its pretensions.

Thomas Jefferson declared the establishment of such

courts to be “diametrically opposite to what we

conceive to be the common rights of nations.” Letter

from Thomas Jefferson to Edmond Charles Genet (c.

July

16,

1793),

https://founders.archives.gov/

documents/Jefferson/01-26-02-0454. He explained, “a

nation has of natural right entire and exclusive

jurisdiction over the territory it occupies.” Id. If it

granted authority to “judges appointed by another

nation, it’s limits depend on the instrument of

cession.” Id. Because the Convention never granted

France the “power … to establish complete courts of

admiralty” in America, France had violated American

sovereignty. Id.

C. The Founders Would Have Regarded This

Lawsuit as Fantastical.

The War of Independence was fought to vindicate

the American view that the British Parliament (which

governed England and Scotland) could neither tax

American colonies—who each had their own

legislatures—nor regulate their commerce. As just

one example, the Stamp Act Congress denied

Parliament’s authority to tax the colonies. In its

petition, it asserted that only colonial assemblies

could tax the peoples of America. See Resolutions of

the Stamp Act Congress, Resol. V (Oct. 19, 1765), in

Documents of American History 57, 58 (7th ed. 1963)

(“[T]hat no taxes ever have been, or can be

constitutionally imposed on [the people of these

colonies], but by their respective legislatures.”).

26

Patrick Henry introduced a resolve in the Virginia

Assembly that “any person who shall, by speaking or

writing, assert or maintain that any person or persons

other than the General Assembly of this Colony, have

any right or power to impose or lay any taxation on

the people here, shall be deemed an enemy to His

Majesty’s Colony.” Virginia Stamp Act Resolutions

(May 30, 1765), in Documents of American History,

supra, at 55, 56.

Of course, the Declaration of Independence

denounced the King for “combin[ing] with others to

subject us to a Jurisdiction foreign to our

Constitution, and unacknowledged by our Laws;

giving his Assent to their Acts of pretended

Legislation … For imposing Taxes on us without our

Consent.” The Declaration of Independence paras. 14,

18 (U.S. 1776).

We triumphed in our insistence upon American

territorial sovereignty. As noted earlier, the 1783

Treaty with Britain saw it begrudgingly acknowledge

our claim—the United States were “free, sovereign

and Independent States.” Definitive Treaty of Peace,

Gr. Brit.-U.S., supra, art. I, 8 Stat. at 81. Again,

Britain “relinquishe[d] all claims to the government,

propriety and territorial rights of the same, and every

part thereof.” Id.; cf. 1 Story, Commentaries on the

Constitution, supra, at 17 (“By the treaty … Great

Britain relinquished all claim, not only to the

government, but to the ‘propriety and territorial

rights of the United States[.]’”). After the 1783 Treaty,

Britain could no longer claim to govern us, via

Parliament or by common law tort rules.

27

Every other nation that recognized the United

States was implicitly doing the same. They were

recognizing our nation’s sovereign territorial rights to

govern ourselves. Likewise, by establishing relations

with foreign nations, the United States (including

every single constituent State) was recognizing the

same territorial rights in other nations. When we

recognize a foreign nation, we implicitly disclaim any

pretension to rule it.

Imagine the withering American reaction had

Imperial Britain adopted Boulder’s view of a

sovereign’s regulatory reach. Suppose that in 1784,

after the Treaty of Paris, the British Parliament

passed liability rules to better govern our guns,

militias, and army. Under Boulder’s theory,

notwithstanding Britain’s recognition of our

sovereignty and independence, Britain could have

done this, because every sovereign could regulate any

activity that affects it, despite the action occurring in

another sovereign’s territory. Further, France, Spain,

and the Maratha Confederacy might have legislated

for us as well and sued Americans in their courts for

actions wholly in America. Such assertions of

legislative power would have been unimaginable to

any of the Founders. A nation that rightfully paid a

“decent Respect to the Opinions of Mankind,” The

Declaration of Independence para. 1, would never

implicitly adopt such an indecent, aggressive theory

of legislative power for its constituent States, one that

surges past territorial boundaries and flows

unchecked all over the globe.

To conclude, the principle that a State’s

legislative authority is tied to its territory is an

28

essential feature of our federalism and the

international order. Territorial limits ensure that the

people of Colorado have the right to govern Colorado,

and that the people of Texas have the same right over

Texas. The territorial limits of sovereignty also ensure

that the people of America, rather than the

governments of Russia or China, rule America.

Boulder’s theory of liability would eradicate those

limits by ignoring Colorado’s and America’s borders,

plunging the Nation into the interstate and

international discord the Framers sought to avoid.

III. National Pork Producers Reaffirmed

Territorial Limits on Sovereignty.

Recently, in National Pork Producers Council v.

Ross, the Court addressed a Dormant Commerce

Clause challenge to a California law prohibiting the

in-state sale of pork from pigs “confined in a cruel

manner.” 598 U.S. 356, 365–366 (2023). The National

Pork Producers Council argued that this law had the

practical effect of regulating out-of-state conduct by

“impos[ing] substantial new costs” on out-of-state

pork producers who sought to sell their products in

California. Id. at 371. It claimed that the Court’s

precedents established an “almost per se” bar on such

“extraterritorial effects.” Id. at 373 (cleaned up). The

Court rejected that argument, observing that “[i]n our

interconnected national marketplace, many (maybe

most) state laws have the practical effect of controlling

extraterritorial behavior.” Id. at 374 (cleaned up).

Unlike California’s law in National Pork

Producers, Boulder’s lawsuit does not merely involve

the indirect extraterritorial effects of in-state

regulation of sales and production within Colorado.

29

Boulder’s lawsuit is a prime example of direct

extraterritorial regulation. Boulder, via Colorado law,

seeks to attach liability for oil and gas production and

use outside of Colorado. Fossil fuel producers cannot

escape liability by eschewing the Colorado market, as

pork producers could with respect to California.

More importantly, National Pork Producers

reaffirmed the territorial limits on state legislative

power. The majority observed that its decision did “not

mean to trivialize the role territory and sovereign

boundaries play in our federal system.” Id. at 375. To

the contrary, in “carrying out [the] task” of

“referee[ing] disputes about where one State’s

authority ends and another’s begins,” “this Court has

recognized the usual legislative power of a state to act

upon persons and property within the limits of its own

territory.” Id. (cleaned up). That beneficial limit, the

Court said, is “a feature of our constitutional order

that allows different communities to live with

different local standards.” Id. (cleaned up).

By insisting that Colorado law should apply

across the nation, Boulder seeks to topple that

salutary “constitutional order,” one where each

distinct community may adopt its own standards.

Were Boulder to prevail, the boundaries between the

States would be but lines on a colorful map and we

would have replaced beneficial self-rule with what

best can be described as regulatory anarchy.

The core of Boulder’s claim is that worldwide

greenhouse gas emissions alter the atmosphere,

raising temperatures. By regulating extraterritorial

production, Boulder effectively assumes legislative

power over worldwide fossil fuel production and

30

greenhouse gas emissions. If Boulder’s disruptive

theory of the Constitution is to be believed, Boulder,

Montana may likewise invoke Montana tort liability

rules to regulate production and emission in Colorado,

the entire territory of the United States, and around

the globe. Furthermore, if Boulder’s theory of

extranational regulation is sound, foreign sovereigns

may regulate production and emission within the

United States. The Rock, a city in Australia, might

regulate the inhabitants of Boulder, Colorado. Indeed,

Australia and hundreds of foreign sovereigns may

regulate the many Boulders in the United States and

every other inch within it. In short, Boulder’s suit, if

sanctioned, would hardly be a novel exception to the

hallowed rule of territorial sovereignty. It would

pulverize that rule, leaving only rubble.

*

*

*

*

*

Justice Kennedy once observed that “Federalism

was our Nation’s own discovery. The Framers split the

atom of sovereignty.” U.S. Term Limits, Inc. v.

Thornton, 514 U.S. 779, 838 (1995) (Kennedy, J.,

concurring). Boulder invites this Court to do one

better. Boulder seeks a truly extraordinary act of

fission, requesting this Court to shatter state and

federal sovereignty into thousands of pieces, where

every State of the Union (and its sub-jurisdictions)

and every foreign nation (and its sub-jurisdictions)

can assert regulatory power over every square inch of

America, and every square centimeter of the world.

The parts cannot exercise legislative control over

the whole nation; Boulder must yield to the

constitutional design of exclusive territorial

sovereignty. The parts certainly cannot control the

31

whole world; Boulder’s pretensions must yield to the

realities of international law, and the constitutional

design predicated on that order.

What Boulder seeks is not the vindication of

Colorado’s sovereignty; what it seeks is the hasty,

unthinking distention of it. Ironically, if Boulder

prevails, the result will be the effective obliteration of

Colorado’s sovereignty. Neither Colorado nor the

United States will long enjoy sovereignty or

independence once other States and nations pursue

the same schemes, as they inevitably will. The Court

should save Boulder from itself.

CONCLUSION

This Court should reverse the judgment below.

Respectfully submitted,

JENNIFER K. HARDY

Counsel of Record

BOYDEN GRAY PLLC

800 Connecticut Ave NW,

Suite 900

Washington, DC 20006

(202) 955-0620

jhardy@boydengray.com

Counsel for Amicus Curiae

May 21, 2026