The U.S. Supreme Court opened its new term Oct. 5 by hearing arguments in Suncor Energy (U.S.A.) Inc. v. County Commissioners of Boulder County, a closely watched case that could affect climate-related lawsuits around the country. Boulder County and the city of Boulder sued Suncor Energy and ExxonMobil under Colorado law, seeking compensation for alleged local harms associated with climate change. The Colorado Supreme Court ruled in 2025 that federal law did not preclude the claims from proceeding.
During oral arguments, the justices focused heavily on whether Boulder’s lawsuit should be viewed as a traditional state tort action seeking compensation for local injuries or, as the energy companies contend, an effort to use Colorado law to regulate the consequences of worldwide greenhouse-gas emissions. Justice Brett Kavanaugh focused on Supreme Court precedents treating interstate pollution as a matter of federal law. When Suncor’s attorney said Boulder was relying on Colorado law — the law of the affected state — Kavanaugh responded, “Okay. That resolves this case.” (Oral Arg. Tr. at 38.) Kavanaugh nevertheless immediately asked counsel to address an important wrinkle: the court’s precedent allowing claims under the law of the pollution’s source state.
The companies also faced questions about whether the dispute is sufficiently developed for the Supreme Court to resolve now. Justice Ketanji Brown Jackson said the discussion made her think “that we’re really early in this case, that this is sort of premature from the standpoint of this Court exercising its jurisdiction.” (Oral Arg. Tr. at 52.) She noted that other federal defenses remain pending and questioned whether there had yet been a state-court determination concerning which state’s law applies. (Oral Arg. Tr. at 52–53.) Later, Jackson returned to the factual record, questioning whether Colorado itself might qualify, at least in part, as a source state because it has emitters or refineries. (Oral Arg. Tr. at 79–82.)
Chief Justice John Roberts pressed Boulder on the distinction it drew between regulating emissions and imposing tort liability for fossil-fuel production and alleged deception. After Boulder’s attorney acknowledged that federal law significantly occupies the field of greenhouse-gas emissions, Roberts asked, “isn’t your suit an attempt to evade those decisions?” and characterized the litigation as “an effort to reduce emissions.” Boulder’s attorney disputed that characterization, arguing that its deception theory would not prevent the companies from continuing to produce fossil fuels if consumers were properly informed about their consequences. (Oral Arg. Tr. at 96–97.)
The potential reach of state tort liability also drew attention. Kavanaugh questioned why a tort suit should be treated differently from state legislation aimed at the same conduct, warning that enough such suits could “bankrupt” defendants and observing that potentially “any manufacturer, any business” could face similar claims. (Oral Arg. Tr. at 107.) Boulder responded that traditional tort law has long permitted states to impose liability for in-state injuries resulting from conduct occurring elsewhere, even when that liability may influence the defendant’s future conduct. (Oral Arg. Tr. at 107–08.)
Ultimately, the argument asked the following for consideration: whether Colorado’s claims are conventional state-law actions seeking damages for injuries within the state or an impermissible attempt to impose Colorado law on conduct and emissions occurring around the world; and whether the court should resolve that question at this stage of the litigation. Justice Samuel Alito recused himself from participating in the matter, leaving eight justices to decide it. Listen to the oral argument or read the transcript.
Read prior Law Week articles:
Does SCOTUS have jurisdiction in Suncor climate case?
Justice Alito recuses himself from Colorado Suncor Energy case
U.S. Supreme Court to hear Colorado case arguments on opening day, election day