State-Law Climate Tort Suits and Suncor Energy (U.S.A.) Inc. v. County Commissioners of Boulder County: A Primer for Congress

State-Law Climate Tort Suits and Suncor Energy (U.S.A.) Inc. v. County Commissioners of Boulder County: A Primer for Congress

State-Law Climate Tort Suits and Suncor Energy (U.S.A.) Inc. v. County Commissioners of Boulder County: A Primer for Congress

September 30, 2026 (R49419)
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Contents

A Brief History of Climate Tort Suits

The Displacement of Federal Common Law

Suncor and Other Post-AEP State-Law Climate Tort Suits

The U.S. Supreme Court's Jurisdiction to Hear Suncor

Statutory Jurisdiction

Merits Arguments in Suncor

"Equal Sovereignty" and "Extraterritoriality" Preemption

Foreign Affairs Preemption

Statutory Preemption

Considerations for Congress

Summary

Over the last decade, state and local governments have filed dozens of state-law tort suits against energy companies, arguing that those companies are liable for the localized effects of climate change because they misled the public about their products' impact on the climate, thereby inflating demand for fossil fuels, boosting atmospheric concentrations of greenhouse gases, and worsening climate-related harms. The City and County of Boulder, CO, filed one such suit, naming as defendants Suncor and Exxon Mobil. On October 5, 2026, the U.S. Supreme Court is scheduled to hear oral arguments on whether Boulder's suit can proceed.

This case has generated substantial interest from Congress and other government actors. Nearly 200 members and more than 40 states have signed on to amicus briefs supporting either Boulder or Exxon Mobil and Suncor, and the U.S. Department of Justice has filed a brief siding with the energy companies.

According to Suncor and Exxon Mobil, Boulder's suit is an attempt to impose tort liability under Colorado law for greenhouse gas emissions occurring wholly outside Colorado's borders, a form of extra-territorial regulation that exceeds the scope of state power in the federal system. Suncor and Exxon Mobil also argue that state-law tort claims like Boulder's are preempted by the Clean Air Act (42 U.S.C. §§ 7401–7671q), which, they say, provides the exclusive means of addressing pollution that crosses state borders and thus precludes Boulder's suit.

Boulder argues that Suncor and Exxon Mobil lack standing to challenge Boulder's suit, which has not yet proceeded to trial, and, according to Boulder, has not yet inflicted any legally cognizable harm. Boulder also contests the Supreme Court's statutory jurisdiction to hear this case, arguing that there is no final state-court judgment for the Court to review. On the merits, Boulder contends that its suit is a constitutionally permissible exercise of state police power to regulate deceptive marketing and sales practices. Because the Clean Air Act addresses neither marketing nor sales, Boulder argues that the act does not preempt its claims.

Congressional purpose "'is the ultimate touchstone' of preemption analysis." Cipollone v. Liggett Group, Inc., 505 U.S. 504, 516 (1992) (quoting Malone v. White Motor Corp., 435 U.S. 497, 504 (1978)). Thus, if desired, Congress could enact legislation resolving the statutory preemption dispute now before the Court. To that end, Congress could affirmatively authorize suits like Boulder's, or, alternatively, expressly preempt those suits, in part or in whole. Two bills introduced in the 119th Congress would employ the latter approach, barring "any suit in law or equity that is brought against any person engaged in the energy business that seeks . . . relief for alleged past or future harm resulting directly or indirectly from climate change." Stop Climate Shakedowns Act of 2026, H.R. 8330, 119th Cong. (as introduced by House, Apr. 16, 2026); Stop Climate Shakedowns Act of 2026, S. 4340, 119th Cong (as introduced by Senate, Apr. 16, 2026). Congress may also refrain from action, accepting the federal judiciary's resolution of cases or controversies.

On October 5, 2026, the Supreme Court will hear oral arguments in Suncor Energy (U.S.A.) Inc. v. County Commissioners of Boulder County (Suncor).¹ The issue before the Court is whether the City and County of Boulder, CO (collectively, Boulder), can sue energy companies under state law to recover monetary compensation for harms attributable to climate change. The defendant energy companies—Suncor and Exxon Mobil (collectively, Suncor)—portray Boulder's suit and dozens of similar, currently pending suits across the country² as an existential threat to the fossil-fuel industry and argue that these suits are foreclosed by the Constitution, the Clean Air Act, or both.³ Some Members of Congress, a coalition of states, and the U.S. Department of Justice (DOJ) have filed amicus briefs joining these arguments.⁴ Other Members of Congress and a different coalition of states join Boulder in arguing that Suncor lacks standing to challenge Boulder's suit, that the Supreme Court lacks jurisdiction to hear this case, and that Boulder's suit is not barred by the Constitution or by statute.⁵ This report summarizes relevant history of climate-related litigation, surveys the arguments now before the Supreme Court, and identifies considerations for Congress.

A Brief History of Climate Tort Suits

The arguments now before the Court in Suncor are rooted in past attempts to address climate change using tort law. To understand those arguments, it is necessary to situate Suncor in the broader, decades-long sweep of climate-based tort litigation.

A tort is an act or omission that inflicts legally cognizable harm on another.⁶ Tort law, in turn, is the body of rules that define the elements of, and remedies for, various torts.⁷ Historically, these rules evolved through common law, which means that they were created by judges through case-by-case adjudication, typically in state, rather than federal, court.⁸ As with "common law generally," tort law "adapts to changing scientific and factual circumstances."⁹ Thus, while many torts originated from disputes between private property owners, they evolved over time to encompass suits brought by state and local governments on behalf of large numbers of their citizens.¹⁰ These included suits seeking the abatement of environmentally harmful activities.¹¹ By the early 2000s, some litigants began suing major emitters of greenhouse gases (GHGs), arguing that those emitters were liable for nuisance because of their impact on the climate.¹²

The Displacement of Federal Common Law

American Electric Power (AEP) v. Connecticut was among this first wave of climate tort suits.¹³ The plaintiffs in that case—state and local governments and nonprofit land trusts—sought a court order compelling the defendants—a group of electric power producers—to reduce their GHG emissions.¹⁴ The plaintiffs brought their case in federal district court, arguing that the defendants were liable under the "federal common law" of nuisance, or alternatively under state nuisance law.¹⁵ The dispute in AEP centered on the first of those two legal theories.

Unlike state courts, federal courts "do not possess a general power" to create common law by "develop[ing] and apply[ing] their own rules" to decide cases.¹⁶ Congress can authorize courts to create federal common law, but absent statutory authorization, federal courts can fashion their own rules of decision only when resolving cases where no federal statute governs, and where it "would be inappropriate" to apply state law because of some significant conflict between "uniquely federal interests" or "the basic scheme of the Constitution," and the operation of state law.¹⁷ Because those conditions will rarely obtain, federal common law applies only in "narrow areas."¹⁸

In Illinois v. City of Milwaukee (Milwaukee I), the Supreme Court identified one such area.¹⁹ In that case, Illinois sued to abate Milwaukee's discharge of sewage to Lake Michigan, a body of water "bounded . . . by four States."²⁰ According to the Court, the interstate nature of the case "touch[ed] basic interests of federalism" and implicated "an overriding federal interest" in a "uniform rule of decision."²¹ Thus, the Court declared, "[w]hen we deal with air and water in their ambient or interstate aspects, there is a federal common law."²²

That pronouncement was short-lived. Five months after Milwaukee I, Congress passed the Federal Water Pollution Control Act Amendments of 1972, commonly known as the Clean Water Act (CWA).²³ Less than nine years later, the Supreme Court held in City of Milwaukee v. Illinois (Milwaukee II) that the CWA had displaced the federal common law of interstate water pollution recognized in Milwaukee I.²⁴ In so holding, the Court stressed that federal law "is generally made not by the federal judiciary . . . but by the people through their elected representatives in Congress."²⁵ The Court thus began "'with the assumption' that it is for Congress, not federal courts, to articulate the appropriate standards to be applied as a matter of federal law."²⁶ Reasoning from this premise, the Court held that Congress need only "sp[eak] directly to," and "address[]" an issue to remove that issue from the realm of federal common law.²⁷ Applying that rule, the Court concluded that the CWA's "all-encompassing program of water pollution regulation" had displaced "often vague and indeterminate nuisance concepts" as the source of "appropriate federal standards" and thus displaced the federal common law of interstate water pollution.²⁸

The Court's decision in Milwaukee II framed the dispute in AEP, where the primary issue was whether the Clean Air Act (CAA) had displaced federal common law claims regarding interstate GHG emissions.²⁹ Four years before AEP, the Supreme Court held in Massachusetts v. EPA that GHGs were pollutants within the meaning of the CAA, but as of 2010, when AEP reached the Supreme Court, EPA had not exercised its authority under the CAA to regulate GHG emissions from power plants.³⁰ Until EPA did so, the plaintiffs argued, federal common law remained intact.³¹

The Supreme Court rejected that argument. According to the Court, it was "plain that the Act 'speaks directly' to emissions of carbon dioxide from the defendants' plants," and that Congress had "delegated to EPA the decision whether and how to regulate" those emissions.³² That "delegation is what displaces the federal common law," the Court stressed, and it would continue to do so even if EPA "declined to regulate" powerplant GHG emissions "altogether."³³

With any federal common law of interstate GHG pollution displaced, the Court explained that the viability of plaintiffs' state-law tort claims would depend, in part, on whether those claims were superseded (i.e., "preempted") by the CAA.³⁴ Because no party had "briefed preemption or otherwise addressed the availability of a claim under state nuisance law," the Court declined to resolve whether climate tort suits could proceed under state law.³⁵

Suncor and Other Post-AEP State-Law Climate Tort Suits

Testing the proposition that AEP left unresolved, state and local governments have since filed dozens of state-law climate tort suits against energy companies.³⁶ These more recent suits largely rest on claims of deceptive marketing and allege that producers and sellers of fossil fuels affirmatively misled the public about their products' impacts on the climate and produced and sold fossil fuels in quantities that they knew to be dangerous.³⁷ The plaintiffs seek monetary compensation for localized climate-related harms like drought, flooding, and extreme heat, but, unlike the plaintiffs in AEP, they do not seek court orders requiring defendants to reduce emissions.

Boulder brought one such suit. That case commenced in 2018, when Boulder filed its complaint against Suncor in Colorado state trial court.³⁸ Suncor then sought to transfer the case from state to federal court through a procedure known as "removal."³⁹ Defendant energy companies filed similar removal motions in many similar state-law tort suits across the country. Years of removal litigation ensued.⁴⁰

Eventually, every federal appeals court to consider the matter—the U.S. Courts of Appeals for the First, Second, Third, Fourth, Eighth, Ninth, Tenth, and D.C. Circuits—concluded that state-law climate tort suits belonged in state, rather than federal, court.⁴¹ The defendant energy companies asked the Supreme Court to review those judgments in at least eight separate petitions for certiorari, including one filed by Suncor.⁴² The Court denied each of those petitions, leaving climate tort suits in the state courts where they were originally filed.⁴³

Back in state courts, the defendant energy companies, including Suncor, moved to dismiss. In these motions, the defendants argued, among other things, that the state-law claims against them were preempted by the Constitution and the CAA, violated their constitutional rights to due process, and impermissibly discriminated against out-of-state commercial activity in violation of the dormant Commerce Clause.⁴⁴

In several courts, the defendants prevailed.⁴⁵ Other courts, including the Colorado state trial court presiding over Boulder's suit against Suncor, denied the motions to dismiss, allowing claims to proceed.⁴⁶

Suncor sought review of that denial in the Colorado Supreme Court through a procedural mechanism called a "petition for a rule to show cause" under Rule 21 of the Colorado Appellate Rules.⁴⁷ In response, the Colorado Supreme Court agreed to consider Suncor's preemption arguments, but not its other grounds for dismissal.⁴⁸

Following briefing and argument, a five-to-two majority of the Colorado Supreme Court rejected Suncor's preemption arguments and remanded to the trial court for further proceedings.⁴⁹

Suncor then petitioned the U.S. Supreme Court for review of the Colorado Supreme Court's judgment, asking the Court to consider "[w]hether 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."⁵⁰ DOJ took the unusual step of filing an unsolicited amicus brief supporting Suncor's petition⁵¹—this despite having filed a brief during the previous Administration in which it opposed a similar petition for certiorari in a different climate tort suit.⁵²

The Court granted Suncor's petition but also directed the parties to brief "[w]hether the Court has statutory and Article III jurisdiction to hear this case."⁵³

The U.S. Supreme Court's Jurisdiction to Hear Suncor

Suncor raises novel questions about the scope of state power in the federal system, the nature of federal common law, and the preemptive scope of the CAA. However, to reach those questions the Court must first conclude that Suncor has standing to bring suit, and that the Court has jurisdiction under 28 U.S.C. § 1257(a) to hear that suit.

Standing

Article III of the Constitution limits the exercise of federal judicial power to specified classes of "Cases" and "Controversies."⁵⁴ The Supreme Court has interpreted this "case or controversy" language to require a party seeking relief in federal court to establish a sufficiently "personal stake" in the outcome of the case.⁵⁵ That stake is known as standing. If a litigant lacks standing, then federal courts, including the Supreme Court, lack jurisdiction to hear that litigant's case.⁵⁶

According to the Court, a litigant can establish standing to appeal—i.e., appellate standing—by "demonstrat[ing] that it has suffered an [(1)] actual or imminent injury that is [(2)] 'fairly traceable' to the judgment below and that [(3)] could be 'redress[ed] by a favorable ruling.'"⁵⁷ The parties dispute whether Suncor can establish the first of those elements: injury.⁵⁸

Suncor argues that the Colorado Supreme Court's judgment inflicted two cognizable injuries.⁵⁹ First, Suncor notes that the judgment below binds state courts in Colorado and thus deprives it of its federal preemption defense in both Boulder's suit and any future climate tort suit in the state.⁶⁰ Suncor contends that this outcome adversely altered its tangible legal rights, a form of harm that the Supreme Court deemed sufficient for appellate standing in a case called ASARCO Inc. v. Kadish.⁶¹ Second, Suncor claims that the decision below will force it to incur costs defending Boulder's suit, which it describes as "a classic pocketbook injury" that independently gives rise to standing.⁶²

Boulder argues that ASARCO is distinguishable because the lower court judgment at issue in that case definitively invalidated mineral leases.⁶³ In Boulder's view, the Colorado Supreme Court's judgment inflicted no comparably concrete injury when it rejected one of Suncor's many defenses. While conceding that Suncor would have standing to appeal a final judgment holding it liable for damages, Boulder dismisses that outcome as "entirely speculative" and thus insufficiently imminent to confer standing.⁶⁴ Boulder also disputes Suncor's "pocketbook injury."⁶⁵ Although economic harm is a quintessential standing injury,⁶⁶ the Supreme Court has rejected claims of appellate standing where the asserted economic injury—an award of attorneys' fees—was "only a byproduct of the suit itself."⁶⁷ According to Boulder, that reasoning forecloses litigation costs as a basis for standing.⁶⁸

Statutory Jurisdiction

The parties also dispute the Court's statutory jurisdiction to hear Suncor's appeal. The Constitution authorizes Congress to define the scope of the Supreme Court's appellate jurisdiction.⁶⁹ "Since 1789," Congress has allowed the Court to review state court judgments "only after the highest state court in which judgment could be had has rendered a '(f)inal judgment or decree.'"⁷⁰ In general, a state court decision is "final" if it is "an effective determination of the litigation and not of merely . . . intermediate steps therein."⁷¹

This finality limitation on the Supreme Court's appellate jurisdiction is codified today at 28 U.S.C. § 1257(a). The parties dispute whether the Colorado Supreme Court's decision—which addressed Suncor's preemption defense but not the ultimate question of Suncor's liability—was "final" within the meaning of § 1257(a) or was instead a non-final order resolving a mid-case, or "interlocutory," appeal.⁷²

Arguing that the decision was final, Suncor invokes two Supreme Court precedents: Atlantic Richfield v. Christian⁷³ and Cox Broadcasting Corp. v. Cohn.⁷⁴

Atlantic Richfield concerned the finality of a Montana Supreme Court judgment that upheld a trial court's denial of a motion for summary judgment in a state tort suit.⁷⁵ There, as here, the state supreme court did not resolve tort liability and remanded to the trial court for further proceedings.⁷⁶ Still, the U.S. Supreme Court unanimously held that the Montana Supreme Court's decision was final, and thus reviewable.⁷⁷ What mattered, the U.S. Supreme Court reasoned, was that the decision was issued through "a supervisory writ proceeding," which Montana law treats as "a self-contained case," rather than an appeal in an ongoing suit.⁷⁸ Because the Montana Supreme Court's judgment resolved what was effectively "a separate lawsuit," the U.S. Supreme Court deemed it final.⁷⁹

So too here, argues Suncor.⁸⁰ Rule 21 of the Colorado Appellate Rules describes the state supreme court's resolution of a petition for a rule to show cause as the "final determination of [an] original," rather than an appellate, proceeding.⁸¹ Similarly, the Colorado Supreme Court described its action on Suncor's Rule 21 petition as an "original" proceeding, and as an exercise of its "original" jurisdiction.⁸² According to Suncor, that framing conclusively establishes that the Colorado Supreme Court's proceeding was a new, self-contained case, thus rendering the court's judgment final for purposes of § 1257(a).⁸³

According to Boulder, Suncor elevates "mere off-hand labels" over substance.⁸⁴ Observing that the Colorado Supreme Court sometimes characterizes Rule 21 proceedings as original, and sometimes as appellate, Boulder maintains that the state court's reference to "original jurisdiction" should not carry the dispositive weight that Suncor accords it.⁸⁵ Boulder also argues that Atlantic Richfield is distinguishable.⁸⁶ In its view, the Montana Supreme Court's supervisory writ proceeding was "self-contained" and thus distinct from the underlying tort litigation because that proceeding ran against the Montana trial court itself, which was a named party before the state supreme court.⁸⁷ By contrast, Boulder argues that the proceeding before the Colorado Supreme Court concerned only the correctness of a lower court order, making that proceeding essentially no different from the exercise of appellate jurisdiction over a preexisting case.⁸⁸ Because the Colorado Supreme Court did not dispose of that preexisting case, Boulder maintains that the state court's decision was not final.⁸⁹

If Atlantic Richfield does not control, Suncor argues in the alternative that statutory jurisdiction is proper under Cox Broadcasting.⁹⁰ There, the U.S. Supreme Court identified four categories of cases in which it had previously asserted appellate jurisdiction over state supreme court judgments that "finally determined the federal issue" in a case but did not resolve the underlying case.⁹¹ Suncor invokes only the fourth Cox Broadcasting category, which encompasses cases in which (1) "the party seeking [Supreme Court] review . . . might prevail on the merits on nonfederal grounds" in ongoing state proceedings "thus rendering unnecessary review of the federal issue by th[e] Court"; (2) "reversal of the state court on the federal issue would be preclusive of any further litigation on the relevant cause of action"; and (3) "a refusal immediately to review the state-court decision might seriously erode federal policy."⁹²

Suncor argues that all three elements are satisfied here because (1) it may prevail in Colorado trial court on state-law defenses that the Colorado Supreme Court did not address; (2) success before the U.S. Supreme Court would result in dismissal of the underlying tort suit; and (3) preemption arguments necessarily implicate federal policy interests.⁹³

According to Boulder, this case satisfies none of the applicable Cox Broadcasting elements.⁹⁴ Echoing arguments that DOJ used when opposing certiorari in an earlier climate tort suit,⁹⁵ Boulder contends that the first of those elements is not met where, as here, the party seeking Supreme Court review might prevail on additional federal grounds that the state supreme court did not address.⁹⁶ According to Boulder, the second Cox Broadcasting element is lacking because Suncor's preemption defense applies only to suits concerning interstate emissions.⁹⁷ Thus, even if Suncor prevailed, Boulder argues that it could still seek relief for harms attributable to in-state emissions. Reversal of the state court judgment would therefore limit but not "preclu[de] . . . litigation on the relevant cause of action."⁹⁸ Finally, Boulder argues that Suncor has identified no federal policy interest that would authorize review of an interlocutory decision despite § 1257(a)'s express limitations.⁹⁹

If enough Justices agree with Boulder's jurisdictional arguments, then Suncor's petition for certiorari will be "dismissed as improvidently granted," a disposition that would leave in place the Colorado Supreme Court's decision and would allow Boulder's suit to proceed in state trial court.¹⁰⁰ If five Justices side with Suncor on jurisdiction, then the Court could proceed to the merits and consider the parties' arguments regarding federal preemption.¹⁰¹

Merits Arguments in Suncor

Suncor argues that Boulder's claims are preempted by the Constitution for either of two reasons. First, Suncor claims that state-law climate tort suits are impliedly preempted by "equal sovereignty" and "extraterritoriality" principles that derive from "constitutional structure" and that gave rise to the erstwhile federal common law of interstate pollution.¹⁰² Second, Suncor contends that Boulder's suit is independently barred by the doctrine of foreign affairs preemption, which safeguards the federal government's exclusive constitutional authority to make foreign policy.¹⁰³ Constitution aside, Suncor also argues that the CAA preempts Boulder's claims.¹⁰⁴

"Equal Sovereignty" and "Extraterritoriality" Preemption

In Milwaukee I and AEP, the Supreme Court described the federal common law of interstate pollution as arising from, respectively, "basic interests of federalism,"¹⁰⁵ and the "demands" of the "basic scheme of the Constitution."¹⁰⁶ However, the Court has not otherwise articulated a constitutional basis for that now-displaced body of law. Suncor asks the Court to do so now. In its primary preemption argument, Suncor maintains that the federal common law of interstate pollution sprang from two related but distinct structural constitutional principles.¹⁰⁷ First, Suncor points to a "principle of equal sovereignty" that precludes states from exercising certain sovereign powers that they surrendered upon joining the union, including, Suncor says, the power to use their own laws to abate pollution in other jurisdictions.¹⁰⁸ Second, Suncor invokes a "principle of extraterritoriality" and claims that that principle bars states from regulating conduct that occurs wholly outside their borders.¹⁰⁹

According to Suncor, Congress's enactment of the CWA and CAA did not alter these underlying constitutional principles, which retain their preclusive effect notwithstanding statutory displacement of federal common law.¹¹⁰ Displacement, in other words, did not render state law competent to resolve disputes about interstate pollution. Rather, Suncor argues, any dispute that would have been subject to federal common law of interstate pollution is presumptively preempted by the equal sovereignty and extraterritoriality principles that gave rise to federal common law in the first place.¹¹¹ On Suncor's theory, Congress can rebut this presumption of preemption if it authorizes state-law regulation of interstate pollution—something Congress can do because its enumerated powers are not subject to the same constitutional constraints as state authority.¹¹² However, if Congress wishes to elevate state law in this way, then Suncor insists that Congress must do so using "exceedingly clear language," as when Congress alters the balance between federal and state power by legislating in an area of traditional state control.¹¹³

Applying these principles, Suncor argues that because climate change is attributable to worldwide GHG emissions and because Boulder seeks redress for harms attributable to climate change, Boulder effectively seeks to regulate out-of-state GHG emissions through the imposition of state-law tort liability.¹¹⁴ According to Suncor, that makes this suit the kind of dispute that, before the enactment of the CAA, would have been governed by federal common law of interstate pollution.¹¹⁵ As such, Suncor argues that this suit is preempted by the constitutional principles that underpin federal common law unless Congress states otherwise. In Suncor's view, Congress did not do so, and Boulder's suit should be dismissed.¹¹⁶

Boulder disagrees. To start, it argues that Suncor's theory of constitutional preemption conflicts with Supreme Court precedent, particularly International Paper Co. v. Ouelette.¹¹⁷ There, the Court considered whether, following the CWA's displacement of federal common law of interstate water pollution, Vermont could bring a state-law tort suit to abate pollution that originated in New York.¹¹⁸ As Boulder observes, the Court in Ouelette made no mention of the equal sovereignty and extraterritoriality principles that Suncor invokes here. Instead (as discussed below), the Court looked to the CWA, not the Constitution, and ultimately concluded that Congress intended to preempt some, but not all, state tort suits.¹¹⁹ According to Boulder, that reasoning and holding demonstrates that, once federal common law is displaced, state law causes of action are viable unless Congress preempts them—not the other way around, as Suncor would have it.¹²⁰

Even if Suncor were right, and the scope of displaced federal common law defined the scope of constitutional preemption, Boulder argues that it would still win because its suit falls outside of that scope.¹²¹ In Boulder's telling, federal common law governed suits by or against states that sought to abate pollution in other states. By contrast, Boulder describes its suit as a dispute between two non-state actors that targets Suncor's allegedly tortious marketing and sales practices, not its GHG emissions.¹²² According to Boulder (and the Colorado Supreme Court), such claims are squarely within the ambit of state authority and not federal common law.¹²³

More fundamentally, Boulder maintains that Suncor's constitutional preemption arguments misconceive the scope of state tort law.¹²⁴ According to Boulder, Suncor's theory risks federalizing a wide swath of tort litigation, including suits for defamation, defective product, or internet fraud, all of which seek redress for injuries in one state arising from conduct in another.¹²⁵ The better approach, Boulder insists, is to police the constitutional bounds of permissible state tort suits by relying on well-established principles grounded in the text of the Due Process, Full Faith and Credit, and Commerce Clauses, none of which Suncor invokes here.¹²⁶

Foreign Affairs Preemption

Suncor next argues that Boulder's claims are barred by foreign affairs preemption.¹²⁷ That doctrine embodies the principle that "at some point an exercise of state power that touches on foreign relations must yield" to the federal government's authority to control foreign policy, which the Constitution vests exclusively in Congress and the President.¹²⁸

The Supreme Court has suggested, and some lower courts have held, that the scope of foreign affairs preemption depends on the nature of the state action at issue.¹²⁹ On this understanding, if a state action reflects the exercise of a traditional state power, then it will be subject to foreign affairs preemption when "there is evidence of clear conflict" between that action and an express federal policy reflected in official documents, like executive agreements or treaties.¹³⁰ If, however, a state law "intrudes on the field of foreign affairs without addressing a traditional state responsibility," then it may be preempted "even absent any affirmative federal activity in the subject area of the state law, and hence without any showing of conflict."¹³¹

Because the parties disagree about whether Boulder's suit is an exercise of traditional state power, they disagree about the showing required to establish foreign affairs preemption. According to Suncor, Boulder's suit is an attempt to regulate GHG emissions in other countries, a regulatory power that no state has ever possessed and one that could undermine the federal government's foreign affairs prerogatives and strain relations with other countries whose corporations could be named as defendants in state-law climate tort suits.¹³² For its part, Boulder frames its suit as an exercise of the traditional state police powers to regulate deceptive marketing and sales practices in the United States.¹³³ According to Boulder, because Suncor identifies no clear conflict with a federal policy outlined in statute, treaty, or executive agreement, that suit can proceed.¹³⁴

Statutory Preemption

Constitution aside, the parties dispute whether climate tort suits like Boulder's are preempted by the CAA. The Constitution makes federal law supreme, but whether a particular federal statute preempts, rather than coexists with, an overlapping body of state law is a question of congressional intent as discerned primarily from statutory text.¹³⁵ Preemption can be express but it is often implied, as when a federal statutory scheme is so pervasive that it leaves no room for parallel state law, or when a state law hinders implementation of a federal law. ¹³⁶

The Supreme Court has never addressed whether the CAA preempts state tort suits. However, in Ouellette (discussed above), the Court analyzed preemption under the CWA, a statute that parallels the CAA in several ways.¹³⁷ For instance, both laws employ a cooperative federalism model in which Congress sets national requirements that states can implement and enforce within their borders through EPA-approved state-law air and water programs that meet minimum federal requirements.¹³⁸ Both laws also contain savings clauses that (1) authorize states to adopt air and water regulations that go beyond the federal minimum standards, and (2) preserve rights of injured parties to seek relief under state "statute or common law" causes of action.¹³⁹

The question before the Court in Ouellette was whether this statutory scheme preempted Vermont from suing under its own tort law to limit water pollution from a factory in New York.¹⁴⁰ Concluding that Vermont's suit was impliedly preempted, the Court stressed that the CWA assigned regulatory authority to "source" states, that is, to states in which pollution originates.¹⁴¹ In the Court's view, allowing downstream "affected" states like Vermont to use their own laws to regulate pollution in source states would subvert the CWA's goals of "efficiency and predictability" by exposing regulated entities to multiple, potentially contradictory bodies of state law.¹⁴² While that conflict sufficed to preempt Vermont's tort suit, the Court read the CWA's savings clauses to "negate[] the inference" that Congress meant to preempt all state tort law.¹⁴³ Thus, the Court held that affected states like Vermont remained free to bring tort suits under the law of source states.¹⁴⁴

All federal courts of appeals to consider the matter—the Third, Fourth, and Sixth Circuits—have held that Ouellette's reasoning and holding apply with equal force to the CAA and that litigants can therefore address harms from out-of-state air pollution using the tort law of the source state but not the affected state.¹⁴⁵ Suncor and Boulder disagree about whether this rule applies here, and if it does, which way it cuts.

According to Suncor, Boulder attempts to use affected-state law to regulate out-of-state GHG emissions, an exercise in cross-border regulation that is essentially no different from the Vermont tort suit at issue in Ouellette.¹⁴⁶ Like that suit, Suncor argues that Boulder's suit conflicts with Congress's statutory scheme, which tasks EPA with deciding whether and how to set GHG emissions standards, and authorizes EPA-approved states to implement those standards, but only within their borders.¹⁴⁷

According to Boulder, Suncor's preemption theory is undercut by EPA's assertion in a recent rulemaking that it lacks authority under the CAA to regulate GHG emissions, at least from mobile sources.¹⁴⁸ In any case, Boulder argues that Ouellette is inapposite because there is no conflict between its suit, which seeks to regulate marketing and sales, and the CAA, which does not address those behaviors.¹⁴⁹ If Ouellette controls, however, then Boulder insists that the decision resolves this case in its favor.¹⁵⁰ The question before the Court is "whether federal law precludes state-law claims," and Ouellette held that such claims may proceed under the law of the source state.¹⁵¹ Claiming that its complaint did not identify which state's common law would apply, Boulder insists that under Ouellette, the Supreme Court's "only option is to affirm and allow the Colorado courts to resolve the choice of law issue in due course."¹⁵²

Considerations for Congress

Congress can refrain from action and allow the judiciary to determine the viability of suits like Boulder's. Alternatively, if desired, Congress could address the issues in Suncor by legislatively dictating whether and how climate tort suits can proceed. To that end, Congress could employ any of at least three approaches. First, acting pursuant to its power under the Commerce Clause,¹⁵³ Congress could broadly preempt suits like Boulder's, as in two proposed bills in the 119th Congress that would bar "any suit in law or equity that is brought against any person engaged in the energy business that seeks . . . relief for alleged past or future harm resulting directly or indirectly from climate change."¹⁵⁴ Second, also acting pursuant to the Commerce power, Congress could instead explicitly authorize such suits. This authorization would clarify the CAA's preemptive effect and directly address Suncor's primary constitutional preemption argument, though state-law climate tort suits might remain vulnerable to foreign affairs preemption challenges, which rest, in part, on the Constitution's assignment to the President of certain foreign affairs powers. Third, Congress could authorize state-law climate tort suits while restricting the scope of available claims, capping relief, and requiring suits to proceed in certain courts—limits on liability and litigation that Congress has imposed in several other contexts.¹⁵⁵

Congress could apply any of these three approaches to address not just state tort law, but also state "climate Superfund" laws, which use statutory formulas, rather than tort-law principles, to hold energy companies liable for the costs of responding to climate change.¹⁵⁶ To date, only Vermont and New York have enacted such laws,¹⁵⁷ but other states are considering similar measures.¹⁵⁸ Both Vermont's and New York's laws have been challenged in court, and two federal district courts recently invalidated New York's law based on reasoning that closely tracks several of Suncor's arguments to the Supreme Court.¹⁵⁹

The prospect of climate-related liability under state law has implications for another issue of long-standing congressional interest: whether to limit EPA's authority to regulate GHGs under the CAA. Since the Supreme Court held in Massachusetts v. EPA that GHGs were pollutants under the CAA,¹⁶⁰ Members have introduced multiple bills that would have prevented EPA from issuing rules targeting GHG emissions.¹⁶¹ If enacted, such bills could undermine CAA-based preemption arguments like those advanced by Suncor. However, Congress could mitigate that risk by pairing limits on EPA's regulatory authority with language that expressly preempts state-law regulation of GHG emissions.

Footnotes

1. | No. 25-170 (U.S. docketed Aug. 12, 2025).

2.

E.g., In re Fuel Indus. Climate Cases, No. S288664 (Cal.); Delaware v. BP Am. Inc., No. N20C-09-97 (Del. Super. Ct.); Hawaii v. BP p.l.c., No. 1CCV-25-717 (Haw. Cir. Ct.); City & County of Honolulu v. Sunoco LP, No. 1CCV-20-380 (Haw. Cir. Ct.); County of Maui v. Sunoco LP, No. 2CCV-20-283 (Haw. Cir. Ct.); City of Chicago v. BP p.l.c., No. 2024CH1024 (Ill. Cir. Ct.); Maine v. BP p.l.c., No. PORSC-CV24-442 (Me. Super. Ct.); Minnesota v. Am. Petroleum Inst., No. 62-CV-20-3837 (Minn. Dist. Ct.); Platkin v. Exxon Mobil Corp., No. MER-L-1797-22 (N.J. Super. Ct.); City of Hoboken v. Exxon Mobil Corp., No. HUD-L-3179-20 (N.J. Super. Ct.); Town of Carrboro v. Duke Energy Corp., No. 24CV3385-670 (N.C. Super. Ct.); County of Multnomah v. Exxon Mobil Corp., No. 23-cv-25164 (Or. Cir. Ct.); Rhode Island v. Shell Oil Prods. Co., No. PC-2018-4716 (R.I. Super. Ct.); King County v. BP p.l.c., No. 18-2-11859-0 (Wash. Super. Ct.).

3. | Brief for the Petitioners, Suncor, No. 25-170 (U.S. May 14, 2026).

4.

Brief of House Majority Leader Steve Scalise and 102 Other Members of Congress as Amici Curiae in Support of Petitioners, Suncor, No. 25-170 (U.S. May 21, 2026); Brief of Sens. Ted Cruz, Chuck Grassley, Mike Lee, and Ted Budd as Amici Curiae in Support of Petitioners, Suncor, No. 25-170 (U.S. May 21, 2026); Brief of Alabama, West Virginia, and 24 Other States as Amici Curiae in Support of Petitioners, Suncor, No. 25-170 (U.S. May 21, 2026); Brief for the United States as Amicus Curiae Supporting Petitioners, Suncor, No. 25-170 (U.S. May 21, 2026).

5.

Brief of Sen. Sheldon Whitehouse, Rep. Pramila Jayapal, and 88 Additional Members of Congress as Amici Curiae in Support of Respondents, Suncor, No. 25-170 (U.S. Aug. 3, 2026); Brief of Colorado, California, and 17 Other States as Amici Curiae in Support of Respondents, Suncor, No. 25-170 (U.S. Aug. 3, 2026); Brief for Respondents, Suncor, No. 25-170 (U.S. July 27, 2026).

6. | Tort, Black's Law Dictionary (12th ed. 2024).
7. | CRS In Focus IF11291, Introduction to Tort Law, by Andreas Kuersten (2023).
8. | Common Law, Black's Law Dictionary (12th ed. 2024)
9. | Am. Elec. Power Co. (AEP) v. Connecticut, 564 U.S. 410, 423 (2011).
10. | Jonathan H. Adler, Displacement and Preemption of Climate Nuisance Claims, 17.2 J. L., Econ. & Pol'y 217–62 (2022).
11. | E.g., Georgia v. Tenn. Copper Co., 206 U.S. 230 (1907); New Jersey v. City of New York, 283 U.S. 473 (1931).
12. | Native Village of Kivalina v. ExxonMobil Corp., 696 F.3d 849, 854 (9th Cir. 2012); AEP, 564 U.S. at 418.
13. | AEP, 564 U.S. at 410.
14. | Id. at 419.
15. | Id. at 418. Nuisance, Wex, Cornell L. Sch., https://www.law.cornell.edu/wex/nuisance [https://perma.cc/8MX6-NFNE] (last visited Sep. 17, 2026).
16. | City of Milwaukee v. Illinois (Milwaukee II), 451 U.S. 304, 312 (1981) (citing Erie R. Co. v. Tompkins, 304 U.S. 64, 78 (1938)).
17. | AEP, 564 U.S. at 421, 422; Boyle v. United Techs. Corp., 487 U.S. 500 (1988).
18. | Wheeldin v. Wheeler, 373 U.S. 647 (1963); Texas Indus., Inc. v. Radcliff Materials, Inc., 451 U.S. 630 (1981).
19. | Milwaukee I, 406 U.S. 91 (1972), superseded by statute, Federal Water Pollution Control Act Amendments of 1972, Pub. L. No. 92-500, 86 Stat. 816 (codified as amended at 33 U.S.C. §§ 1251–1376), as recognized in AEP, 564 U.S. 410.
20. | Id. at 105 n.6.
21. | Id. (citing Banco Nacional de Cuba v. Sabbatino, 376 U.S. 398, 421–27 (1964)).
22. | Id. at 103.
23. | Federal Water Pollution Control Act Amendments of 1972, Pub. L. No. 92-500, 86 Stat. 816 (codified as amended at 33 U.S.C. §§ 1251–1376).
24. | Milwaukee II, 451 U.S. 304 (1981).
25. | Id. at 313 (citing Wallis v. Pan Am. Petroleum Corp., 384 U.S. 63, 68 (1966)).
26. | Id. at 316 (quoting Jones v. Rath Packing Co., 430 U.S. 519, 525 (1977).
27. | Id. at 315.
28. | Id. at 318.
29. | AEP v. Connecticut, 564 U.S. 410, 420–29 (2011).
30. | Massachusetts v. EPA, 549 U.S. 497, 528–29 (2007).
31. | AEP, 564 U.S. at 425–26.
32. | Id. at 424.
33. | Id. at 426.
34. | Id. at 429.
35. | Id.
36. | See, e.g., case cites supra note 2.
37. | E.g., Mayor of Balt. v. BP p.l.c., 353 A.3d 1142, 1150 (Md. 2026); City & County of Honolulu v. Sunoco LP, 537 P.3d 1173, 1181 (Haw. 2023); County of San Mateo v. Chevron Corp., 32 F.4th 733, 741 (9th Cir. 2022), cert. denied, 143 S. Ct. 1797 (2023) (mem.).
38. | Complaint and Jury Demand, Bd. of Cnty. Comm'rs of Boulder County v. Suncor Energy (U.S.A.) Inc., No. 2018CV30349 (Colo. filed Apr. 17, 2018).
39. | Notice of Removal, Bd. of Cnty. Comm'rs of Boulder County v. Suncor Energy (U.S.A.) Inc., No. 18-cv-01672 (D. Colo. June 29, 2018). For more on removal, see CRS Legal Sidebar LSB11213, Removal to Federal Court of Cases Against Federal Officials and Agents, by Joanna R. Lampe (2024).
40. | See Anne Arundel County v. BP p.l.c., 94 F.4th 343, 346 (4th Cir. 2024) (describing energy companies' repeated attempts at removal as "display[ing] a real commitment to the maxim, 'If at first you don't succeed, try, try, again.'")

41.

Rhode Island v. Shell Oil Products Co., LLC., 35 F.4th 44 (1st Cir. 2022), cert. denied, 143 S. Ct. 1796 (2023) (mem.); Connecticut v. Exxon Mobil Corp., 83 F.4th 122 (2d Cir. 2023); City of Hoboken v. Chevron Corp., 45 F.4th 699 (3d Cir. 2022), cert. denied, 143 S. Ct. 2483 (2023) (mem.); Anne Arundel County, 94 F.4th at 343; Minnesota v. Am. Petroleum Inst., 63 F.4th 703 (8th Cir. 2023); City & County of Honolulu v. Sunoco LP, 39 F.4th 1101 (9th Cir. 2022), cert. denied, 143 S. Ct. 1795 (2023) (mem.); Bd. of Cnty. Comm'rs of Boulder County v. Suncor Energy (U.S.A.), Inc., 25 F.4th 1238 (10th Cir. 2022), cert. denied, 143 S. Ct. 1795 (2023) (mem.); District of Columbia v. Exxon Mobil Corp., 89 F.4th 144 (D.C. Cir. 2023).

42.

Petition for Writ of Certiorari, Shell Oil Products Co., LLC., v. Rhode Island, No. 22-524 (U.S. docketed Jan. 5, 2023), cert. denied, 143 S. Ct. 1796 (2023) (mem.); Petition for Writ of Certiorari, Chevron Corp. v. City of Hoboken, No. 22-821 (U.S. docketed Feb. 27, 2023), cert. denied, 143 S. Ct. 2483 (2023) (mem.); Petition for Writ of Certiorari, BP p.l.c. v. Mayor of Balt., No. 22-361 (U.S. docketed Oct. 14, 2022), cert. denied, 143 S. Ct. 1795 (2023) (mem.); Petition for Writ of Certiorari, Am. Petroleum Inst. v. Minnesota, No 23-168 (U.S. docketed Aug. 18, 2023), cert. denied, 144 S. Ct. 620 (2024) (mem.); Petition for Writ of Certiorari, Chevron Corp. v. City of Oakland, No. 20-1089 (U.S. docketed Jan. 8, 2021), cert. denied, 141 S. Ct. 2776 (2021) (mem.); Petition for Writ of Certiorari, Chevron Corp. v. San Mateo County, No. 22-495 (U.S. docketed Nov. 28, 2022), cert. denied, 143 S. Ct. 1797 (2023) (mem.); Petition for Writ of Certiorari, Sunoco LP v. City & County of Honolulu, No. 22-523 (U.S. docketed Dec. 6, 2022), cert. denied, 143 S. Ct. 1795 (2023) (mem.); Petition for Writ of Certiorari, Suncor Energy (U.S.A.) Inc. v. Bd. of Cnty. Comm'rs of Boulder Cnty., No. 21-1550 (U.S. docketed June 8, 2022), cert. denied, 143 S. Ct. 1795 (2023) (mem.).

43. | See sources cited supra note 41.
44. | Order re Defendants' Motions to Dismiss, Bd. of Cnty. Comm'rs of Boulder Cnty. v. Suncor Energy (U.S.A.) Inc., No. 2018CV30349 (Colo. June 21, 2024).

45.

E.g., Order Granting Defendants' Joint Motion to Dismiss Plaintiff's Complaint for Failure to State a Claim and for Lack of Personal Jurisdiction, City of Charleston v. Brabham Oil Co., No. 2020-CP-10-03975 (S.C. Aug. 6, 2025); Decision and Order, Bucks County v. BP p.l.c., No. 2024-01836 (Penn. May 16, 2025); Mayor of Balt. V. BP p.l.c., 353 A.3d 1142, 1150 (Md. Ct. of Appeals 2026).

46. | Order re Defendants' Motions to Dismiss, supra note 44.
47. | Petition for Order to Show Cause Pursuant to C.A.R. 21, In re ExxonMobil Corp., No. 2024SA206 (Colo. July 18, 2024); see Colo. App. R. 21 (2026).
48. | Order and Rule to Show Cause, In re Bd. of Cnty. Comm'rs of Boulder Cnty., No. 2024SA206 (Colo. July 29, 2024).
49. | In re Bd. of Cnty. Comm'rs of Boulder Cnty., 586 P.3d 161 (Colo. 2025).
50. | Petition for Writ of Certiorari, Suncor, No. 25-170 (U.S. docketed Aug. 8, 2025).

51.

John Elwood, No Invitation Necessary: When the Solicitor General Weighs in Unsolicited, SCOTUSblog (Feb. 10, 2026), https://www.scotusblog.com/2026/02/no-invitation-necessary-when-the-solicitor-general-weighs-in-unsolicited/ [https://perma.cc/54D3-5J5R]; Brief for the United States as Amicus Curiae Supporting Petitioner, Suncor, No. 25-170 (U.S. Sep. 11, 2025).

52. | Brief for the United States as Amicus Curiae, Suncor LP v. City & County of Honolulu, No. 23-947 (U.S. Dec. 10, 2024), Petition for Writ of Certiorari, Suncor LP v. City & County of Honolulu, No. 93-947 (U.S. Feb. 28, 2024).
53. | Suncor Energy (U.S.A.) Inc. v. Cnty. Comm'rs of Boulder County, 146 S. Ct. 1605 (2026) (mem.).
54. | U.S. Const. art III; see Libr. of Cong., Overview of Cases or Controversies, Constitution Annotated, https://constitution.congress.gov/browse/essay/artIII-S2-C1-1/ALDE_00013375/ (last visited Sep. 17, 2026).
55. | Lujan v. Defs. of Wildlife, 504 U.S. 555, 559–62 (1992).
56. | Spokeo, Inc. v. Robins, 578 U.S. 330, 337–38 (2016).
57. | Food Mktg. Inst. v. Argus Leader Media, 588 U.S. 427, 432–33 (2019) (quoting Monsanto Co. v. Geertson Seed Farms, 561 U.S. 139, 149 (2010)).
58. | Id.
59. | Brief for the Petitioners, supra note 3, at 20.
60. | Id.
61. | Id. at 20; ASARCO Inc. v. Kadish, 490 U.S. 605, 619 (1989).
62. | Brief for the Petitioners, supra note 3, at 20.
63. | Brief for Respondents, supra note 5, at 11.
64. | Id. at 13.
65. | Id.
66. | Diamond Alt. Energy, LLC v. EPA, 606 U.S. 100, 111 (2025).
67. | Diamond v. Charles, 476 U.S. 54, 70–71 (1986).
68. | Brief for the Respondents, supra note 5, at 13.
69. | Libr. of Cong., Supreme Court Appellate Jurisdiction, Constitution Annotated, https://constitution.congress.gov/browse/essay/artIII-S2-C2-4/ALDE_00001221/ (last visited Sep. 17, 2026).
70. | Cox Broad. Corp. v. Cohn, 420 U.S. 469, 477 (1975) (quoting 28 U.S.C. § 1257).
71. | Pierce County v. Guillen, 537 U.S. 129, 140 (2003).
72. | Interlocutory Appeal, Black's Law Dictionary (12th ed. 2024)
73. | 590 U.S. 1 (2020).
74. | 420 U.S. 469 (1975).
75. | Atlantic Richfield v. Mont. Second Jud. Dist. Ct., 408 P.3d 515 (Mont. 2017).
76. | Atlantic Richfield, 590 U.S. at 10.
77. | Id. at 12.
78. | Id.
79. | Id.
80. | Brief for the Petitioners, supra note 3, at 16.
81. | Colo. App. R. 21 (2026).
82. | In re Cnty. Comm'rs of Boulder Cnty., 586 P.3d 161, 167 (2025).
83. | Brief for the Petitioners, supra note 3, at 17.
84. | Brief for Respondents, supra note 5, at 20.
85. | Id.
86. | Id. at 18.
87. | Id.
88. | Id.
89. | Id. at 22.
90. | Brief for the Petitioners, supra note 3, at 18.
91. | Cox Broad. Corp. v. Cohn, 420 U.S. 469, 477 (1975).
92. | Id. at 482–83.
93. | Brief for the Petitioners, supra note 3, at 19.
94. | Brief for Respondents, supra note 5, at 15.
95. | Brief for the United States as Amicus Curiae, Suncor LP. v. City & County of Honolulu, No. 23-947, supra note 52.
96. | Brief for Respondents, supra note 5, at 15.
97. | Id.
98. | Id. (quoting Cox Broad. Corp. v. Cohn, 420 U.S. 469, 482–83 (1975)).
99. | Id. at 16.

100.

Some commentators have speculated that the Court may dismiss a case only with the concurrence of at least one of the Justices who voted to hear the case. Stephen Wemiel, Will the Supreme Court DIG it?, SCOTUSblog (Nov. 21, 2025, at 10:00 ET), https://www.scotusblog.com/2025/11/will-the-supreme-court-dig-it/ [https://perma.cc/DW2K-A76X]. Such an internal procedure would effectively require a sixth vote for dismissal in certain cases. Id.

101. | On September 28, 2026, the Court announced that Justice Alito would recuse himself from Suncor, meaning that the case will be reviewed by eight Justices rather than the usual nine. Letter from Clerk, Suncor Energy (U.S.A.) Inc. v. Cnty. Comm'rs of Boulder Cty., No. 25-170 (U.S. Sept. 28, 2026).
102. | Brief for the Petitioners, supra note 3, at 21–27.
103. | Id. at 39.
104. | Id. at 43.
105. | Milwaukee I, 406 U.S. 91, 105 n.6 (1972).
106. | AEP v. Connecticut, 564 U.S. 410, 421 (2011).
107. | Brief for the Petitioners, supra note 3, at 22–26.
108. | Id. at 23.
109. | Id. at 24.
110. | Id. at 29.
111. | Id. at 30.
112. | Id.
113. | Id. (citing U.S. Forest Serv. v. Cowpasture River Pres. Ass'n, 590 U.S. 604, 621–22 (2020).
114. | Id. at 34.
115. | Id. at 37.
116. | Id. at 33.
117. | Brief for Respondents, supra note 5, at 28; see Int'l Paper Co. v. Ouellette, 479 U.S. 481 (1987).
118. | Int'l Paper Co., 479 U.S. at 491.
119. | Brief for Respondents, supra note 5, at 28; see Ouelette, 479 U.S. at 491–497; id. at 497–98.
120. | Brief for Respondents, supra note 5, at 29.
121. | Id. at 31.
122. | Id. at 32.
123. | Id. at 32–34; In re Cnty. Comm'rs of Boulder Cnty., 586 P.3d 161 (Colo. 2025).
124. | Brief for Respondents, supra note 5, at 34.
125. | Id. at 35, 25.
126. | Id. at 25.
127. | Brief for the Petitioners, supra note 3, at 39.
128. | Am. Ins. Ass'n v. Garamendi, 539 U.S. 396, 413 (2003); United States v. Pink, 315 U.S. 203 (1942).
129. | Garamendi, 539 U.S. at 418–20; Movsesian v. Victoria Versicherung AG, 670 F.3d 1067, 1071–72 (9th Cir. 2012).
130. | Garamendi, 539 U.S. at 418, 421.
131. | Movsesian, 670 F.3d at 1072; Garamendi, 539 U.S. at 418.
132. | Brief for the Petitioners, supra note 3 at 40–42.
133. | Brief for Respondents, supra note 5, at 41.
134. | Id. at 41–42.
135. | See generally CRS Report R45825, Federal Preemption: A Legal Primer, by Bryan L. Adkins, Alexander H. Pepper, and Jay B. Sykes (2023).
136. | Murphy v. NCAA, 584 U.S. 453, 477–79 (2018).
137. | Int'l Paper Co. v. Ouellette, 479 U.S. 481, 483 (1987).
138. | AEP v. Connecticut, 564 U.S. 410, 424 (2011); Ouellette, 479 U.S. at 489.
139. | 42 U.S.C. §§ 7416, 7604(e); 33 U.S.C. §§ 1370, 1365(e).
140. | Ouellette, 479 U.S. at 491.
141. | Id. at 497.
142. | Id. at 496–97.
143. | Id. at 492.
144. | Id. at 497.
145. | Bell v. Cheswick Generating Station, 734 F.3d 188, 197 (3d Cir. 2013); North Carolina ex rel. Cooper v. Tenn. Valley Auth., 615 F.3d 291, 306 (4th Cir. 2010); Merrick v. Diageo Ams. Supply, Inc., 805 F.3d 685, 692 (6th Cir. 2015).
146. | Brief for the Petitioners, supra note 3, at 45–46.
147. | Id.

148.

Brief for Respondents, supra note 5, at 46 (citing 91 Fed. Reg. 7686, 7688 (Feb. 18, 2026)). In response to this argument, Suncor and the United States stressed that EPA had not yet disclaimed statutory authority to regulate GHG emissions from stationary sources, including oil and gas production facilities. Brief for the Petitioners, supra note 3, at 33; Brief for the United States, supra note 5, at 34, n.4. EPA has since issued a proposed rule interpreting the CAA not to authorize regulation of GHG emissions from stationary sources. 91 Fed. Reg. 59002 (Sep. 17, 2026).

149. | Brief for Respondents, supra note 5, at 47.
150. | Id. at 30.
151. | Petition for Writ of Certiorari, Suncor, supra note 50, at I.
152. | Brief for Respondents, supra note 5, at 31.
153. | U.S. Const. art. I, § 8, cl. 3. See also CRS In Focus IF12335, Constitutional Authority Statements: A Quick Guide, by Whitney K. Novak (2023).
154. | Stop Climate Shakedowns Act of 2026, H.R. 8330, 119th Cong. (as introduced by House, Apr. 16, 2026); Stop Climate Shakedowns Act of 2026, S. 4340, 119th Cong (as introduced by Senate, Apr. 16, 2026).

155.

E.g., Volunteer Protection Act of 1997, Pub. L. No. 105-19, § 4, 111 Stat. 219–21 (codified as amended at 42 U.S.C. § 14503); Biomaterials Access Assurance Act of 1998, Pub. L. No. 105-230, § 5, 112 Stat. 1519, 1524 (codified at 21 U.S.C. § 1604) and the Supporting Anti-Terrorism by Fostering Effective Technologies (SAFETY) Act of 2002, Pub. L. No. 107-296, § 863, 116 Stat. 2238, 2239 (codified as amended at 6 U.S.C. § 442).

156. | Rachel Rothschild, State Climate Superfunds, 126 Columbia L. Rev. 585, 656–670 (2026). The Stop Climate Shakedowns Act of 2026, S.4340, would preempt both tort suits and climate Superfund laws.
157. | N.Y. Env't Conserv. §§ 76-0101 to 76-0105 McKinney (2025); Vt. Stat. Ann. tit. 10, §§ 596–599c (2025).
158. | Karen Zraick, Climate 'Superfund' Bills Spread Nationwide, Despite Legal Battles, N.Y. Times (Feb. 6, 2026), https://www.nytimes.com/2026/02/06/climate/climate-superfund-laws-bills.html.
159. | United States v. New York, No. 25-CV-3656 (PKC), 2026 WL 2859471 (S.D.N.Y. Sept. 23, 2026); West Virginia v. James, No. 25-CV-00168 (BKS/DJS), 2026 WL 2568355 (N.D.N.Y. Aug. 31, 2026).
160. | 549 U.S. 497, 528–29 (2007).

161.

E.g., Domestic Manufacturing Act of 2021, S.1326, 117th Cong. (as introduced by Senate, Apr. 22, 2021); Energy Exploration and Production to Achieve National Demand (EXPAND) Act of 2014, H.R. 3895, 113th Cong. (as introduced by House, Jan. 16, 2014); No More Excuses Act of 2013, H.R. 2081, 113th Cong. (as introduced by House June 3, 2013).