Boulder Sued Exxon Over Climate Costs. The Rule Deciding It Is One Thomas Already Wrote.

The Supreme Court opens its new term on October 5 with oral argument in Suncor Energy (U.S.A.) Inc. v. County Commissioners of Boulder County, docket 25-170. The question is whether Colorado's Boulder County can sue two oil companies under state tort law for the cost of adapting to a warmer climate.

Boulder and Boulder County sued Suncor Energy and Exxon Mobil in state court in 2018. The claims are public and private nuisance, trespass, unjust enrichment, and civil conspiracy. One theory holds that selling fossil fuels while knowing they would cause climate harm created liability. A second holds that the industry marketed its products as safe for decades after it understood the risk.

The question the justices added

The Colorado Supreme Court ruled for Boulder in May 2025, in Case No. 24SA206, holding that federal law does not preempt the county's claims. Suncor and Exxon Mobil appealed, and the justices agreed in February to hear the case. They added a second question beyond the one the companies had asked: whether the Supreme Court has statutory and Article III jurisdiction to hear the case at all.

Maggie Gardner, a Cornell Law School professor who tracks the case for the Transnational Litigation Blog, has written that the added question gives the Court a way to avoid the preemption fight directly if it has lost interest in resolving it. Nearly seventy amicus briefs have been filed, a measure of how many outside parties expect the ruling to reach well past Boulder.

Alito steps aside

Justice Alito filed a recusal notice on September 28. It did not state a reason. Alito does not hold stock in Suncor or Exxon Mobil, the companies named in the suit, but he holds stock in ConocoPhillips and Phillips 66, two other oil companies facing their own climate suits elsewhere, and he has stepped aside from cases involving companies he holds stock in before.

The standard Thomas already wrote

The preemption question in Suncor will not be decided from scratch. In April, the Court ruled 6 to 3 in Hencely v. Fluor Corporation, a case over whether a military contractor could be sued under state law for a soldier's death in Afghanistan. Justice Thomas wrote the majority opinion, joined by Justices Sotomayor, Kagan, Gorsuch, Barrett, and Jackson.

The opinion held that state tort claims against a federal contractor are preempted only when the government directed the contractor to do the very thing the lawsuit challenges. Thomas wrote that a uniquely federal interest in regulating military bases overseas does not, by itself, create a conflict with state negligence law when a contractor strays from what the government actually ordered.

Chief Justice Roberts and Justice Kavanaugh dissented in Hencely, joined by Alito, arguing federal interests can displace state tort law even without a government directive covering the specific conduct at issue. Gardner has written that the same reasoning resonates in Suncor. If the Court applies Thomas's own Hencely standard, a company's general knowledge about climate change is a weaker basis for preemption than a government order naming the exact conduct being sued over.

What the vote looks like now

A ruling against Boulder would not stay contained to Colorado. Other cities and counties around the country have filed similar suits making the same production and deception arguments, and most are waiting on a federal preemption answer before their own cases can move. Whether that answer tracks the standard Thomas wrote in April, or the broader one Roberts and Kavanaugh argued for in dissent, will matter to all of them. The vote that decides it does not include the justice who joined that dissent most pointedly and who, this time, is not voting at all.