Supreme Court Hears Landmark Climate Liability Case as Boulder Seeks Damages From Fossil Fuel Giants
Washington — The Supreme Court returned to the bench Monday for the start of a new term, and it immediately took up one of the most closely watched legal battles of the year: whether the city and county of Boulder, Colorado, can pursue state-law claims against some of the nation’s largest fossil fuel producers for the local consequences of global climate change. The case arrives at the high court after years of procedural maneuvering, and the justices’ decision could have sweeping implications for the dozens of similar lawsuits filed by state and local governments across the country.
The dispute is part of a broader wave of litigation in which states, counties, and municipalities have sued energy companies, seeking money damages for the harms caused by the buildup of greenhouse gases in the atmosphere. Boulder’s lawsuit, filed in 2018, targets Exxon Mobil, the country’s biggest energy company, and Suncor Energy, which operates two oil refineries in Colorado. The lawsuit is still in its early stages. The question now before the Supreme Court is not whether Boulder will ultimately win, but whether the case can proceed at all under state law or whether federal law blocks it entirely.
As Jonathan Adler, a law professor at William & Mary who has written extensively about federalism and environmental law, put it, “This is not a judgment about whether these cases will succeed. It’s a judgment about whether folks get to make their case.” Adler, who filed a friend-of-the-court brief supporting Boulder, also noted that even if the city and county are allowed to proceed, the scope of what they can pursue may be substantially narrowed along the way.
Boulder’s lawsuit was originally filed in Colorado state court. The city and county allege that Exxon and Suncor have contributed to climate change through their production and marketing of fossil fuels, forcing Boulder to confront extreme heat, larger and more frequent wildfires, damage to local ecosystems, and other climate-related problems. The complaint raises five claims under state law. Boulder officials argue that the companies’ conduct, including what they describe as deceptive marketing of fossil fuels, has led to “unchecked” use of their products and a rapid rise in greenhouse gas concentrations in the atmosphere.
Exxon and Suncor sought to move the case to federal court, but that effort failed. They then asked the Boulder County District Court to dismiss the case, arguing that federal law forecloses the claims. When the state trial court refused to dismiss, the companies appealed to the Colorado Supreme Court. The state’s highest court sided with Boulder, and the energy companies then appealed to the U.S. Supreme Court.
In agreeing to hear the case, the Supreme Court asked both sides to address two questions: whether federal law precludes Boulder’s state-law claims, and whether the Court even has jurisdiction to review the Colorado Supreme Court’s decision. Only eight of the nine justices participated in Monday’s arguments. Justice Samuel Alito recused himself, as the Court announced last week, without providing a reason. Alito’s financial disclosure for 2025 indicated that he had individual holdings in two energy companies, ConocoPhillips and Phillips 66. He did not report individual stocks in Exxon or Suncor. Because Alito is not participating, there is a possibility the Court could split 4-4. In that scenario, the decision of the Colorado Supreme Court would stand, meaning the case could continue in state court.
Lawyers for Exxon and Suncor argued in their Supreme Court filings that the Constitution and the Clean Air Act bar state-law claims that seek to address harms caused by interstate greenhouse-gas emissions. The Clean Air Act, they said, was not intended to invite state law to govern disputes over interstate pollution. They warned that if the Colorado Supreme Court’s decision is upheld, it would allow all fifty states, tens of thousands of municipalities, and even hundreds of millions of individuals to ask local courts to establish countless and conflicting climate policies for the nation.
The energy companies also received support from the Trump administration, which filed a brief backing Exxon and Suncor. Together, they argued that lawsuits like Boulder’s jeopardize the federal government’s control over foreign affairs. Because greenhouse gases emitted in the United States and abroad mix in the atmosphere, the companies argued that it is impossible to trace emissions back to any particular source. Allowing every state to apply its own laws would lead to confusion and conflict, they said. “It’s a national problem, so it requires a national solution,” said Michael Williams, the solicitor general of West Virginia, during a briefing with reporters.
West Virginia and twenty-five other states have sided with Exxon and Suncor. Williams said those states do not object to a state regulating sources of pollution within its own borders. “So if West Virginia wants to regulate a coal plant in West Virginia, we claim the right to do that,” he said. “In the same way, if Colorado wants to regulate emissions coming from Colorado in Colorado, they’re free to do that as well. What they’re not free to do is say, hey you emitters, anywhere in the world … we’re going to make you pay money for any of those emissions anywhere in the world.”
The energy companies also warned that imposing potentially devastating liability on fossil fuel producers could undercut the United States’ pursuit of primacy in global energy production. Allowing state court judgments to reach emissions released abroad, they argued, would create an “end-run” around diplomatic channels and replace them with innumerable state judicial proceedings.
Boulder, however, urged the Supreme Court to dismiss the appeal for lack of jurisdiction and to allow the case to proceed. In the alternative, lawyers for the city and county argued that the Colorado Supreme Court’s decision should be upheld. “Does anything implicit in the Constitution bar this suit?” they wrote in a filing. “Nothing does.” They noted that courts frequently handle cases involving local harms caused by global or national problems, including food contamination, human trafficking, and the fentanyl crisis. “That climate change is a global problem does not disempower states from redressing its local harms either,” they wrote.
Boulder rejected the companies’ Clean Air Act argument, saying the law regulates emissions but not the conduct of upstream fossil fuel producers. The city and county said they are not suing over emissions broadly but over allegedly deceptive marketing and production practices, which the Clean Air Act does not address. “Indeed, avoiding liability would not require reducing emissions at all — only telling the truth, so the public can make informed consumption decisions free of the distorting effect of petitioners’ misrepresentations,” they argued.
The Trump administration, which has withdrawn the United States from international agreements aimed at addressing climate change, argued that Boulder’s lawsuit invites “needless diplomatic friction” with foreign countries where Exxon and Suncor produce and sell fossil fuels. But Adler, the William & Mary professor, said that argument proves too much. He noted that the administration has pulled out of international climate agreements while simultaneously claiming that lawsuits against energy companies interfere with diplomacy. “If there was an actual conflict between an actual treaty, of course that could preempt state law,” Adler said. “But we don’t even have that.” He also said the foreign-affairs argument would give the executive branch remarkable power to preempt any litigation it dislikes simply by claiming it wants to negotiate about a particular topic. “That can’t be the law,” he said.
Adler also pointed out that Congress could intervene if lawmakers believe these lawsuits are an abuse of the courts. He noted that Congress took similar action in 2005, when it passed a federal law shielding gun manufacturers from civil lawsuits seeking to hold them accountable for harms stemming from the criminal misuse of their firearms. “If Congress believes that what’s going on here is a combination of plaintiffs’ lawyers and activists trying to make energy less available or less affordable, or to otherwise create pressure on fossil-fuel companies, Congress has the tools to address that,” he said. “That’s a job for the legislature, not a job for the courts.”
The stakes in this case are enormous. A ruling for Exxon and Suncor could effectively shut down dozens of similar climate lawsuits filed by state and local governments across the country. A ruling for Boulder would not guarantee that the city ultimately wins its case, but it would allow discovery and a trial on the merits to move forward. It could also open the door to more lawsuits seeking damages from energy companies, with companies potentially facing liability for past and future harms caused by climate change.
Lawyers for both sides appeared before the justices on Monday, and the Court’s decision is expected by the summer of 2027. Until then, the legal fate of Boulder’s climate lawsuit — and potentially many others like it — remains uncertain. What is clear is that the Supreme Court has chosen to wade into one of the most significant environmental and legal questions of the era: who bears responsibility for the local consequences of a global problem? The answer will likely shape climate policy, energy markets, and tort law in the United States for decades to come.
