The US Supreme Court is to hear a climate change case brought by Boulder, Colorado, against Exxon Mobil and Suncor Energy, in a dispute that could determine whether local authorities can pursue fossil-fuel companies in state courts over the alleged costs of global warming.
The case concerns claims filed by the city and Boulder County seeking damages for past and future harm they say has been caused by greenhouse gases released into the atmosphere. The lawsuit remains at an early stage, and the court will not decide whether the claims will ultimately succeed.
Instead, the justices will consider whether federal law prevents the action from proceeding under Colorado law. They have also asked both sides to address whether the court has jurisdiction to review the Colorado Supreme Court’s decision allowing the case to continue.
Boulder filed the lawsuit in 2018, alleging that Exxon and Suncor’s production and allegedly deceptive marketing of fossil fuels had encouraged unchecked use of their products. The city and county say the resulting climate change has contributed to extreme heat, more frequent and severe wildfires and damage to the local ecosystem.
The energy companies tried unsuccessfully to transfer the case to a federal court. They later asked a Colorado trial court to dismiss it, arguing that federal law barred Boulder’s claims, but the request was rejected. The Colorado Supreme Court then sided with the city and county.
Exxon and Suncor have appealed to the US Supreme Court, arguing that the Constitution and the Clean Air Act prevent states from applying their own laws to damage allegedly caused by greenhouse-gas emissions crossing state and national borders.
They warn that allowing Boulder’s case to proceed could enable all 50 states, thousands of municipalities and individuals to bring competing climate claims, creating conflicting policies across the country. The companies argue that only a uniform federal framework can deal with pollution that cannot be separated and traced back to individual sources.
“It’s a national problem, so it requires a national solution,” Michael Williams, West Virginia’s solicitor general, told reporters. West Virginia and 25 other states are supporting Exxon and Suncor, saying the lawsuit could interfere with their own decisions on energy production and environmental protection.
The companies and the Trump administration, which supports their position, have also argued that cases involving emissions released overseas could interfere with the federal government’s management of foreign affairs. They say such litigation risks creating diplomatic friction and undermining the United States’ position in global energy production.
Boulder argues climate change claims should proceed
Boulder has urged the Supreme Court to dismiss the appeal, arguing that it lacks jurisdiction. If the justices reject that argument, the city and county want the Colorado Supreme Court’s ruling to be upheld.
Their lawyers say the action is not an attempt to regulate emissions or create a national climate policy. Instead, they argue, it seeks compensation for local costs allegedly caused by fossil-fuel companies’ conduct, including claims concerning misleading marketing and production practices.
“That climate change is a global problem does not disempower states from redressing its local harms either,” Boulder’s lawyers wrote. They also argue that avoiding liability would not necessarily require companies to reduce emissions, but could instead involve providing truthful information so consumers can make informed decisions.
Jonathan Adler, a law professor at William & Mary who supports Boulder’s position, said the Supreme Court was being asked whether the plaintiffs should be allowed to make their case, rather than whether they would win it.
“This is not a judgment about whether these cases will succeed. It’s a judgment about whether folks get to make their case,” he said, adding that the eventual scope of any litigation could still be significantly narrowed.
Only eight of the nine justices will take part in the arguments after Justice Samuel Alito recused himself. The Supreme Court gave no reason for the decision. His 2025 financial disclosure listed individual holdings in ConocoPhillips and Phillips 66, but not Exxon or Suncor.
His absence means the court could divide four to four. In that event, the Colorado Supreme Court’s decision would remain in force, although it would not establish a wider precedent.
A ruling in the Supreme Court climate change case is expected by summer 2027.
