The US Supreme Court on Monday heard oral arguments in Suncor Energy (U.S.A.) Inc. v. Commissioners of Boulder County, a case brought by the Colorado county against Exxon Mobil and Suncor Energy.

The Court must decide if the federal Clean Air Act preempts the Colorado Consumer Protection Act, and if the Court has jurisdiction to review the Colorado court’s decision. Justice Samuel Alito has recused himself from the case, leaving the case in the hands of the remaining eight justices. In May 2025, the Colorado Supreme Court held that federal law did not preempt state law in the case. The companies then appealed to the US Supreme Court.

In 2018, the County and City of Boulder accused Exxon Mobil and Suncor Energy of altering the climate in Colorado, resulting in damages in the form of costs to reduce the dangers of flooding, wildfires, ground-level ozone, and other related changes. Boulder alleged that the energy companies violated the Colorado Consumer Protection Act, in addition to being unjustly enriched and creating public and private nuisances. The companies tried to transfer the case to federal court, then asked the state trial court to dismiss the case. When both efforts failed, they asked the state Supreme Court to rule on the question of federal preemption, which is where federal law supersedes or overrides conflicting state or local law.

Boulder has asked for monetary relief in the form of compensation for past and future damages, such as the cost of analyzing and mitigating the effects of climate change. The original suit specifically does not ask the court to enjoin the energy companies from any sales or operations in Colorado and does not ask the court to enforce any kind of emissions controls.

According to the energy companies, “Nearly 60 state and local governments have brought such suits, and more continue to be filed…Each case seeks billions of dollars in damages from the defendant energy companies. This is complete chaos. And without this Court’s intervention, the Nation will be left with different environmental standards for every state.”

The Trump administration has filed an amicus curiae (friend of the court) brief on behalf of Exxon Mobil and Suncor Energy. The brief says, “Boulder’s attempt to regulate global emissions
interferes with the Federal Government’s exclusive role in foreign affairs” in addition to arguing in support of the companies’ assertation of federal preemption. Over 50 amicus curiae briefs have been filed in this case, ranging from petroleum industry and environmental groups to US senators and the Coalition of Large Tribes.