Can a city use state tort law to make an energy company pay for climate-related harm - or does federal law prevent those claims from proceeding?
That question is before the U.S. Supreme Court in Suncor Energy (U.S.A.) Inc. v. County Commissioners of Boulder County, scheduled for oral argument on October 5. The case opens the Court’s 2026-27 argument term. No Supreme Court judgment has been rendered. supremecourt.gov
The dispute could have significant consequences for municipal climate litigation. But the Court must also address a threshold question: whether it has jurisdiction to decide this appeal at its current stage.
What Boulder Alleges
Boulder County and the City of Boulder sued Suncor entities and ExxonMobil in April 2018. They seek compensation for alleged climate-related harms under Colorado law.
According to the plaintiffs’ account, the companies knowingly contributed to climate change while concealing product risks and misleading the public. Boulder describes its lawsuit as a claim for the costs of local harm, rather than an attempt to regulate emissions or stop fossil-fuel production. These remain allegations and the plaintiffs’ characterization of their case. Boulder County
The distinction matters. A claim framed around compensation for injury presents a different legal argument from a direct demand to control emissions. Whether that distinction allows these claims to proceed is central to the dispute.
The Federal Pre-emption Question
Suncor and ExxonMobil argue that federal law precludes Boulder’s claims. The Colorado Supreme Court allowed the lawsuit to proceed in May 2025, concluding that federal law did not pre-empt the claims. The U.S. Supreme Court is reviewing that decision. supremecourt.gov
Federal pre-emption concerns whether federal law displaces an otherwise available state-law claim. In this case, the argument brings together local demands for compensation and the consequences of greenhouse-gas emissions across borders.
The competing positions therefore concern more than the scale of the alleged harm. They concern which body of law can supply a remedy and whether Colorado law can support the particular claims pleaded.
Allowing the lawsuit to continue would not, by itself, establish that the defendants are liable. It would leave further questions about proof and remedies to be resolved through the litigation.
Jurisdiction Could Determine the Appeal’s Reach
When granting review on February 23, the Supreme Court expressly directed the parties to brief and argue whether it has statutory and Article III jurisdiction to hear the case. supremecourt.gov
That additional question deserves attention alongside pre-emption. The Court’s authority to review the dispute is a threshold issue, distinct from whether federal law bars Boulder’s claims.
For readers following the hearing, three questions should remain separate:
Jurisdiction: Can the Supreme Court decide this appeal at this stage?
Pre-emption: Does federal law prevent the Colorado claims from proceeding?
Liability: Can the plaintiffs ultimately prove their allegations and establish an entitlement to compensation?
The October 5 argument should not be presented as a trial deciding responsibility for Boulder’s climate-related costs.
Why Canadian Lawyers Should Watch
For Canadian counsel advising energy businesses with U.S. operations, the appeal illustrates how litigation exposure can turn on the interaction between state remedies and federal law.
Its potential significance extends to how future municipal claims are pleaded and how defendants challenge them. A broad pre-emption ruling could restrict a route to compensation. A narrower ruling - or a disposition based on jurisdiction - could leave substantial questions unresolved.
Those are possible implications, rather than predictions about the outcome. The eventual reasons will matter more than a headline announcing that one side “won.”
The decision will address U.S. law. Its relevance to Canadian practice lies principally in cross-border litigation strategy and the assessment of U.S. exposure.
What to Look for Next
The argument transcript will help identify how the justices approach jurisdiction and the scope of the federal-law defence. Questions from the bench, however, should be read cautiously; they do not establish the Court’s final position.
When judgment arrives, the first task will be to identify precisely what the Court decided - and which questions remain open.
For now, Boulder’s demand for compensation has reached the Supreme Court. Whether the Court can decide the appeal, and whether federal law bars the claims, remain unresolved.
Sources: U.S. Supreme Court docket, No. 25-170 and Boulder County’s account of its lawsuit.