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Attorneys representing two Colorado local governments are set for a high-stakes legal showdown over climate change Monday at the U.S. Supreme Court, where they’ll ask justices to allow Boulder’s lawsuit seeking monetary damages from two fossil fuel companies to proceed in state court.

With help from the Trump administration, the two companies, Suncor Energy and Exxon Mobil, have asked the court to step in and quash the lawsuit, which was filed in 2018 by Boulder County and the city of Boulder. The plaintiffs are seeking monetary damages under state tort law “for the substantial role (the companies) played and continue to play in causing, contributing to and exacerbating climate change.”

Monday’s Supreme Court hearing in the case, known as Suncor v. Boulder, follows another unprecedented summer of record heat, extreme drought conditions and destructive wildfire activity impacting communities across Colorado. Boulder’s suit is one of more than 30 similar cases filed to date by state and local governments nationwide as human-caused climate change, mostly the result of fossil-fuel combustion, pushes average global temperatures to dangerous new highs.

“This case is really about who’s going to bear the costs of all of these accelerating effects that we’re experiencing on the front lines here in Colorado,” Chris Winter, an environmental attorney and executive director of the Getches-Wilkinson Center at the University of Colorado School of Law, said in an interview. “Are those costs just going to fall on the shoulders of all of the taxpayers and citizens and our local governments? Or is the oil industry going to be at least partially responsible for their role in contributing to this crisis?”

Exxon and Suncor, a Canadian oil giant that operates Colorado’s only fossil fuel refinery, argue that federal law preempts Boulder’s efforts to hold the companies accountable in state court. The defendants have tried and failed repeatedly to have the case dismissed or removed to federal court, most recently in May 2025, when the Colorado Supreme Court issued a ruling allowing the case to........

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