The US Supreme Court heard arguments on October 5 over whether Boulder, Colorado, can pursue a climate-damage lawsuit against ExxonMobil and Suncor Energy under state law. Reuters reported that the justices questioned both sides as they considered the companies’ appeal. The hearing concerned whether the case can proceed, with no ruling establishing liability or awarding compensation.
Boulder city and county filed the lawsuit in April 2018. According to the county, it alleges the companies knowingly contributed to climate change while concealing their products’ dangers. Colorado’s Supreme Court allowed the claims to continue in May 2025, concluding that federal law did not block them. The companies are challenging that decision in the nation’s highest court.
The companies argue in their court brief that the Constitution and Clean Air Act prevent state-law claims over harms associated with interstate and international greenhouse-gas emissions. They say allowing local juries to decide such claims could produce conflicting national climate policies. Reuters reported that President Donald Trump’s administration supported the companies’ position at the hearing.
Boulder officials say their communities face costs from wildfires, floods, extreme heat and drought, including damage to infrastructure. In a statement after the hearing, the county said its aim was to obtain a contribution to local climate costs, rather than regulate emissions or halt fossil-fuel production. The alleged concealment and responsibility for damages remain claims to be tested in court.
Reuters reported that Chief Justice John Roberts questioned why state lawsuits should be barred when courts allow cases involving other cross-border harms. He also pressed Boulder’s lawyer about the practical consequences if municipalities across the country brought similar cases. AP reported that key justices appeared concerned about the possible breadth of litigation and divided over the federal and state legal questions.
The implications extend beyond Colorado. According to figures from the companies cited by Reuters, nearly 60 state and local governments have brought dozens of similar lawsuits seeking billions of dollars. A decision favoring the companies could lead to many cases being dismissed. The Supreme Court’s official record confirms the October 5 argument; the parties now await its decision on whether this litigation can advance.
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