Supreme Court to weigh Exxon and Suncor bid to block Boulder climate lawsuit

The US Supreme Court is starting its new term on Monday by diving into a high-stakes battle over whether oil companies can be held liable in local courts for the mounting costs of climate change.

The justices will hear arguments in a bid by Exxon Mobil and Suncor Energy to shut down a long-running lawsuit brought by the city and county of Boulder, Colorado. The outcome could determine the fate of dozens of similar lawsuits filed by states and local governments across the country, all seeking to make fossil-fuel producers pay for the local damage of global warming.

Only eight of the nine justices will decide the matter. Justice Samuel Alito has recused himself from the case. While the court did not give a reason, Alito’s 2025 financial disclosures revealed that he owned stock in other energy producers, ConocoPhillips and Phillips 66. His absence raises the stakes significantly: a 4-4 tie among the remaining justices would leave the lower court’s ruling intact, allowing Boulder’s lawsuit to go ahead in Colorado state court.

What is the Boulder climate lawsuit about?

Boulder first filed its lawsuit in 2018, targeting Exxon Mobil, the largest US energy company, and Suncor Energy, which runs two refineries in Colorado. Local officials argue that the companies’ production and allegedly deceptive marketing of fossil fuels led to an unchecked rise in greenhouse gas emissions.

The lawsuit claims this conduct has forced Boulder to pay for the fallout of climate change, including extreme heat, more frequent wildfires, and widespread ecosystem damage. The city and county brought five claims under Colorado state law, arguing that the energy giants should help cover these local costs.

"This litigation is not an attempt to solve climate change," Boulder’s lawyers wrote in their Supreme Court filings. "It merely asks that petitioners bear their fair share of local costs incurred in part because of their tortious conduct." They argue the lawsuit is about deceptive marketing rather than directly regulating emissions, comparing the case to local lawsuits over food contamination or the fentanyl crisis.

Why are Exxon and Suncor appealing?

Exxon and Suncor, backed by the Trump administration and 26 states, argue that climate change is a global issue that cannot be managed by a patchwork of local lawsuits.

They contend that the federal Clean Air Act and the US Constitution prevent states from using local courts to address harms caused by interstate emissions. If the Colorado court's decision is allowed to stand, the companies' lawyers warned it would authorise "the tens of thousands of municipalities" across America to establish conflicting national climate policies.

They also argue that these lawsuits interfere with foreign policy by attempting to regulate emissions produced and sold abroad. Michael Williams, the solicitor general of West Virginia—one of the states backing the energy companies—said that while Colorado has the right to regulate emissions within its own borders, it cannot demand money for emissions released anywhere in the world.

What happens next?

The Supreme Court is expected to issue its ruling by the summer of 2027.

Jonathan Adler, a law professor at William & Mary who filed a brief supporting Boulder, noted that a victory for the Colorado local governments would not mean they automatically win their case. It would simply mean they have the right to argue it in state court, where their claims could still be narrowed.

If federal courts ultimately allow these climate lawsuits to proceed, the battle could shift to Congress. Adler pointed out that lawmakers have the power to step in and shield the energy industry from civil liability, much like they did for gun manufacturers in 2005. Until then, the immediate future of corporate liability for climate change rests with the Supreme Court.