Suncor Energy (U.S.A.) Inc. v. Commissioners of Boulder County (25-170)
- Term
- OT 2026
- Certiorari granted
- 2026-02-23
- Court below
- Supreme Court of Colorado
- Argued
- 2026-10-05
The case in brief
Facts
The city of Boulder, Colorado, and Boulder County sued several energy companies, including Suncor and Exxon Mobil, in Colorado state court in 2018. They brought claims under Colorado law, such as nuisance, trespass and consumer-protection violations, to recover costs they blame on global climate change. After a detour through federal court ended with the case sent back to state court, the state trial court refused to dismiss the case and ruled that federal law did not block the claims. A divided Colorado Supreme Court agreed by a 5-2 vote, and the companies argue that this ruling conflicts with a decision by a federal appeals court in New York. The U.S. Supreme Court agreed to hear the case and heard arguments on October 5, 2026.
Question
Does federal law bar state-law lawsuits seeking money for local harms said to be caused by the effects of greenhouse-gas emissions from other states and countries on the global climate?
Question Presented
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.
Scope of review: In addition to the question presented by the petition, the Court directed the parties to brief and argue whether this Court has statutory and Article III jurisdiction to hear this case. On September 28, 2026, the Court noted that Justice Alito will not continue to participate in this case.
Model prediction
Boulder County 4-4 (58% confidence, raw). Calibrated to the historical base rate: Boulder County 56%.
Case preview
Whether federal law bars a Colorado county and city from using state-law claims to seek compensation from fossil-fuel companies for local harms allegedly caused by global climate change, and whether the Supreme Court has jurisdiction to hear the case at this stage.
Suncor Energy
- The petitioner argues the Court has jurisdiction because the Colorado Supreme Court's ruling ended a self-contained original proceeding, making it a final judgment, and because the ruling injures petitioners by binding pending cases and forcing continued litigation costs.
- The petitioner argues that the Constitution's structure, including equal state sovereignty and limits on regulating beyond a State's borders, makes disputes over interstate air pollution inherently federal, so state law cannot govern climate-change claims.
- The petitioner argues that the Clean Air Act replaced federal common law without authorizing state law to reach interstate emissions, and that suing producers rather than emitters does not change the claims' federal character.
- The petitioner argues the claims would undermine the federal government's exclusive control over foreign affairs by creating an end-run around diplomatic channels for addressing climate change.
- The petitioner argues that, independently, the Clean Air Act preempts the claims because it makes EPA the first decider of emissions standards and gives States only a circumscribed role.
Boulder County
- The respondent argues the Court lacks jurisdiction because the decision below merely declined to dismiss on the pleadings, any injury is speculative, and the appeal was an interlocutory review rather than a separate writ proceeding, regardless of its 'original proceeding' label.
- The respondent argues that precedents such as AEP and Ouellette treated displaced federal common law as leaving only ordinary statutory preemption questions, and that these claims against producers for deceptive marketing never fell within federal common law anyway.
- The respondent argues that nothing implicit in the Constitution bars the suit, since courts have long applied the law of the state of injury to out-of-state conduct, and interstate effects are policed by choice-of-law, personal-jurisdiction, and dormant Commerce Clause limits.
- The respondent argues foreign-affairs preemption requires a clear conflict with an express federal policy in a statute, treaty, or executive agreement, which petitioners have not identified.
- The respondent argues the Clean Air Act does not impliedly preempt the claims because its saving clauses foreclose field preemption and it governs emissions, not upstream production, sales, or deceptive marketing.
The United States: The United States, supporting petitioners, argues the Court has jurisdiction and that both the Constitution (equal sovereignty and the federal foreign-relations power) and the Clean Air Act preclude Boulder's state-law claims seeking to impose liability for worldwide fossil-fuel activity.
How the case got here
The city of Boulder, Colorado, and Boulder County sued energy companies, including Suncor and Exxon Mobil, in Colorado state court in 2018. They asserted state-law claims, including nuisance, trespass, unjust enrichment, consumer-protection violations and civil conspiracy, to recover costs they attribute to global climate change. After federal removal proceedings ended in a remand to state court, the state trial court denied the companies' motion to dismiss and held that federal law did not preclude the claims. On interlocutory review, a divided (5-2) Colorado Supreme Court affirmed, and the petitioners contend that its decision conflicts with the Second Circuit's decision in City of New York v. Chevron Corp.
- 2018-04-17 — Colorado state court: Complaint filed asserting state-law climate-change claims against energy companies
- 2019 — United States District Court for the District of Colorado: Case removed to federal court; motion to remand granted (405 F. Supp. 3d 947 (D. Colo. 2019)). Remand granted (for respondents)
- 2020 — United States Court of Appeals for the Tenth Circuit: Remand order affirmed (965 F.3d 792 (2020)). For respondents
- 2022 — United States Court of Appeals for the Tenth Circuit: On remand from the U.S. Supreme Court for further consideration in light of BP p.l.c. v. Mayor & City Council of Baltimore, remand order affirmed again (25 F.4th 1238 (2022)). For respondents
- Date not stated — Colorado state district court: Claims against Suncor Energy Inc. dismissed for lack of personal jurisdiction. For Suncor Energy Inc.
- Date not stated — Colorado state district court: Motion to dismiss amended complaint denied; court held federal law did not preclude respondents' claims (2024 WL 3204275). For respondents
- Date not stated — Colorado Supreme Court: Petition for interlocutory review (filed by Exxon Mobil, later joined by the Suncor petitioners) granted
- 2025-05-12 — Colorado Supreme Court: Trial court order affirmed by 5-2 vote (2025 WL 1363355). For respondents
- Date not stated — Colorado Supreme Court: Mandate stayed to allow petitioners to seek U.S. Supreme Court review. For petitioners
- 2025-08-08 — Supreme Court of the United States: Petition for certiorari filed
- 2025-09-11 — Supreme Court of the United States: United States files amicus brief
- 2025-11-10 — Supreme Court of the United States: Brief in opposition filed
- 2026-02-23 — Supreme Court of the United States: Certiorari granted
- 2026-08-04 — Supreme Court of the United States: Set for argument on Monday, October 5, 2026.
- 2026-09-28 — Supreme Court of the United States: Letter from Clerk of Court to counsel of record noting that Justice Alito will not continue to participate in this case.
- 2026-10-05 — Supreme Court of the United States: Argued
In the news
Featured coverage: Supreme Court Questions Oil Companies’ Bid to Shut Down Climate Lawsuits — The Wall Street Journal, 2026-10-05. Argued Oct. 5, the first case of the term. ExxonMobil and Suncor, backed by the Justice Department, argue federal law bars Boulder’s claims for climate-change damages; Justice Alito is recused, so eight justices will decide it. The Journal’s report on the opening argument of the term: the oil companies asking the Court to end Boulder’s state-law climate suit faced skeptical questions from several justices.
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