The U.S. Supreme Court heard arguments Monday in a long-running lawsuit by Boulder city and county officials seeking to make ExxonMobil and Suncor Energy help cover climate-related costs. The justices focused on whether federal law blocks the case and whether it is too early for the high court to intervene—not on whether the companies misled the public about climate change, as Boulder alleges. Boulder filed the lawsuit in 2018, arguing that the companies’ conduct left local taxpayers to pay for preparing for and recovering from climate impacts including floods, wildfires and drought. The companies and the Trump administration urged the court to stop the case, contending that federal laws such as the Clean Air Act and prior Supreme Court rulings prevent local courts from hearing it. Lawyer Kannon Shanmugam, representing the companies, warned that allowing Boulder’s claims to proceed could invite thousands of municipalities to seek large damages from fossil fuel producers, potentially shaping national energy policy through jury verdicts. Boulder’s lawyer, Kevin Russell, countered that the lawsuit seeks compensation for alleged deceptive practices, not an order regulating emissions. He argued that companies should bear some of the costs associated with harms caused by their activities. The justices also questioned whether the case was ready for Supreme Court review. Colorado’s Supreme Court cleared the way for it to proceed in May 2025, but it has not gone to trial and no judgment has been issued. Justice Ketanji Brown Jackson suggested the high court might be acting too soon. Other justices, including Brett Kavanaugh, pressed Boulder’s arguments about why earlier rulings should not end the case. Justice Samuel Alito has recused himself. If the remaining justices split 4-4, the Colorado Supreme Court ruling would stand, allowing the lawsuit to continue. The court’s decision is expected in the coming months. A ruling that sharply limits Boulder’s legal theories could also affect more than two dozen similar climate-accountability lawsuits and climate “superfund” laws in Vermont and New York. The case has taken multiple trips through the courts over eight years, and even a ruling that allows it to proceed would leave further legal steps before a jury could hear evidence. Boulder County commissioners attended Monday’s arguments, while Coloradans affected by wildfires and drought rallied outside the court. Marta Loachamin, a Boulder County commissioner, said communities should not have to shoulder climate-related costs alone. Jenny Singer-Rupp, a Louisville resident who lost her home in the 2021 Marshall fire, urged the justices to let the evidence be heard. Former county commissioners Deb Gardner and Elise Jones, who supported launching the lawsuit in 2018, also traveled to Washington for the arguments.