US Supreme Court to open term with climate damages dispute, with oil-company liability still undecided

The US Supreme Court is scheduled to open its new term at 10 a.m. Eastern time on October 5 with the climate damages dispute brought by the city and county of Boulder against ExxonMobil and Suncor Energy. Its official calendar lists No. 25-170 first. Oral argument had not begun at publication, and this review will not directly calculate how much compensation the companies should pay.¹

AI-generated illustration: climate damages claims and energy-company liability.

How a local damages claim became a federalism dispute

Boulder's city and county filed suit in April 2018, alleging that the companies knew about the climate risks of fossil fuels but concealed the dangers, misled the public and worsened local damage through production and sales. The local governments want the companies to share public costs arising from climate impacts. These remain the plaintiffs' allegations, rather than established findings of corporate wrongdoing.²

On May 12, 2025, the Colorado Supreme Court allowed the relevant state-law claims to proceed. They involve public and private nuisance, trespass, unjust enrichment and civil conspiracy. The court held that federal law did not preempt those claims, while expressly declining to assess their ultimate merits. The companies' failure to secure dismissal at that stage therefore did not mean Boulder had won compensation.³

ExxonMobil and Suncor's central argument is that greenhouse-gas emissions cross state and national borders, so one state's damages rules cannot indirectly govern worldwide activity. They invoke the Constitution's allocation of federal and state powers, federal authority over foreign affairs and the Clean Air Act in seeking reversal of the state high court's decision.⁴ The Trump administration supports the companies in its amicus brief, arguing that these claims would interfere with the federal emissions-regulation system.⁵

Boulder's response stresses that its claims target corporate conduct and misleading marketing, rather than asking judges to set emissions standards directly, and that state law ordinarily provides remedies for local injuries. The dispute thus turns in part on the boundary between emissions regulation and corporate tort liability. Whether that distinction holds is one of the substantive questions in the case.⁶

The Court must first establish whether it can intervene now

A procedural issue could also change the case's course. When granting review on February 23, the Supreme Court directed the parties to address not only whether federal law precludes the state-law claims, but also whether the Court has statutory and Article III jurisdiction. Agreeing to hear the appeal did not resolve that question.⁷

Boulder argues that the state court merely declined to dismiss the relevant claims at the pleading stage, that no final judgment exists and that other defenses remain available, making Supreme Court review premature. The companies argue that the Colorado Supreme Court completed a separately reviewable proceeding and finally decided their federal defense, satisfying the requirements for review.⁶⁴ If the Supreme Court finds jurisdiction lacking, it could avoid deciding the substantive federal-preemption question, leaving the local claims and broader legal dispute to continue.

The bench has also changed. A September 28 letter from the Supreme Court clerk to counsel confirms that Justice Samuel Alito will no longer participate. It gives no reason, and the change alone offers no basis for predicting the outcome.⁸

National consequences depend on the ruling's reach

In their May 14 brief, the companies said nearly 60 state and local governments had filed similar lawsuits. That is a count of governments bringing litigation, not the number of cases consolidated before the Supreme Court, and certainly not a tally of nearly 60 final damages awards.⁴

The parties' positions suggest different possible consequences. A broad acceptance of the companies' federal-law defenses could create higher barriers for similar claims elsewhere. A narrower ruling, or one confined to jurisdiction, would affect those cases differently. Even permission to proceed would leave questions of proof, causation and damages for later litigation. This hearing therefore does not mean that all climate cases will be dismissed together, or that the companies have already been found liable.³⁶

Reuters reported on October 4 that a decision was expected by the end of June 2027. That is a reporting expectation, not a judgment date announced by the Court.⁹ For energy companies and local public finances, the immediate stakes are whether state-law climate-cost claims can advance to consideration on their merits, and where legal authority lies among levels of government. Any actual compensation remains a matter for later proceedings.

Source notes

1. Published 2026-08-04; amended 2026-09-14 · Monthly Argument Calendar October 2026 · Supreme Court of the United States ↩

2. 2026-09-28 · U.S. Supreme Court to Hear Boulder Climate Case Monday · Boulder County; public statement by a party to the litigation ↩

3. 2025-05-12 · Colorado Supreme Court opinion, 2025 CO 21, Appendix A to the petition · Colorado Supreme Court; pp. 1a–24a ↩ ↩²

4. 2026-05-14 · Brief for Petitioners · Suncor Energy and ExxonMobil; party submissions, nearly 60 governments on p. 6 ↩ ↩² ↩³

5. 2026-05-21 · Brief for the United States as Amicus Curiae Supporting Petitioners · US Department of Justice ↩

6. 2026-07-27 · Brief for Respondents · City and County of Boulder; docket filing date, corrected version uploaded August 3 ↩ ↩² ↩³

7. Accessed 2026-10-05 · Docket for 25-170 · Supreme Court of the United States; review granted February 23, 2026 ↩

8. 2026-09-28 · Letter to Counsel in No. 25-170 · Office of the Clerk, Supreme Court of the United States ↩

9. 2026-10-04 · US Supreme Court to kick off term with bid by Big Oil to toss climate suits · Reuters, John Kruzel and Andrew Chung; syndicated by Investing.com ↩