Supreme Court hears Boulder climate case as Alaska backs oil companies

The U.S. Supreme Court heard argument Monday, Oct. 5, in a climate damages suit brought by Boulder County, Colorado, against Suncor Energy and Exxon Mobil. Alaska is one of 26 states backing the companies.

Acting Attorney General Cori Mills signed the Alabama-led brief for Alaska on May 21. It says "our Constitution does not allow two small localities like these to set national energy policy." Alaska also joined a 26-state brief in September 2025, under then-Attorney General Stephen Cox, urging the court to take the case. The United States backs the companies, which say nearly 60 state and local governments have filed similar suits.

Both sides cite the 2012 Ninth Circuit decision in Native Village of Kivalina v. ExxonMobil Corp. Kivalina is an Iñupiaq community on a barrier island in northwest Alaska, where the EPA says reduced sea-ice protection and permafrost thaw have worsened storms, flooding and water-supply problems. The states cite the ruling to argue that displacing a federal right to sue also displaces the remedy. Boulder notes that Exxon's brief in that earlier appeal said damages claims by non-sovereigns fall outside federal common law. Alaska went unmentioned at Monday's argument, and Kivalina is not a party to this case.

Boulder County and the City of Boulder sued in Colorado state court in 2018, claiming nuisance, trespass, unjust enrichment and civil conspiracy. They seek damages, not limits on company operations. The Colorado Supreme Court ruled in May 2025 that the Clean Air Act does not override the claims. The U.S. Supreme Court took the case Feb. 23, adding a jurisdiction question. Justice Alito withdrew from the case Sept. 28, leaving eight justices to decide it.

Kannon Shanmugam, arguing for the companies, called the suit "an unprecedented effort to use state law to regulate global conduct." Sarah Harris, arguing for the United States, said Colorado could "hold oil companies liable for all their fossil fuel activities worldwide." Kevin Russell, arguing for Boulder, said the power to preempt such suits belongs to "Congress, not the courts." Justice Kavanaugh called interstate pollution a federal matter. Chief Justice Roberts noted that suits over in-state injury remain available. Justice Jackson asked whether the court should wait for state courts to rule first. Justice Sotomayor raised the question of forfeiture.

No ruling date has been set. The court could also dismiss the case on jurisdictional grounds without reaching the merits.