The Supreme Court heard arguments Monday in Boulder's climate damages lawsuit against oil companies, a case the Trump administration says exceeds state power and risks suits nationwide.
On Oct. 5, 2026, the Court took up Suncor Energy v. Boulder County and asked a basic federalism question: can a city and county use state court to make oil and gas firms pay for climate-related costs?
Billions of dollars hang in the balance. So do dozens of similar cases filed in recent years by governments in largely blue-leaning areas. A win for Suncor and ExxonMobil could shut those suits down. A tie vote would leave in place a Colorado high court ruling that already cleared Boulder's case to proceed.
The Associated Press reported the arguments as the Court opened its new term on Capitol Hill. Justice Samuel Alito was absent after recusing himself a week earlier over stock ownership in oil companies. That absence raised the chance of a deadlock.
Chief Justice John Roberts zeroed in on what happens if Boulder prevails. Local governments across the country could copy the playbook overnight.
"Presumably, if you prevail, the next day, a municipality in every single state will file a lawsuit. How do you think that will work out on the ground?"
Roberts also pressed for a limiting principle. He said he was not sure what set this case apart from other state-court suits with nationwide reach.
Justice Brett Kavanaugh went further on the target list. A Boulder win, he suggested, would not stop at oil companies.
"I mean, anyone is a potential defendant for a suit like this. Any manufacturer, any business."
That is the core problem conservatives see in this wave of litigation. Progressive localities are trying to set national energy and climate policy through damage verdicts instead of through Congress.
Kannon Shanmugam, the attorney for the energy companies, did not deny the scale of the climate debate. He rejected the courtroom as the place to run it.
"Climate change is certainly one of the most pressing issues" facing the country, but the lawsuit "is exactly the wrong way to go about" addressing it.
Shanmugam told the justices the case tries to use courts for public policy that belongs to Congress and elected officials. He urged them to reverse the Colorado high court ruling that let the suit move forward.
Principal Deputy Solicitor General Sarah Harris, arguing for the Trump administration, backed the companies. She said Boulder's case "egregiously exceeds" the state's authority. The county, in the administration's view, casts itself as a victim of conduct that largely occurred outside Colorado and then tries to project state law across the country.
Companies and the administration also lean on the Clean Air Act. That federal law, they argue, gives the national government, not state courts, the power to regulate emissions. Lawsuits like Boulder's, they say, are an unconstitutional attempt to regulate planet-warming emissions by another name.
Boulder city and county first sued in 2018. Their lawyer, Kevin Russell, told the Court the suit is not an effort to regulate emissions or halt production. Boulder wants the companies held accountable for allegedly misleading the public about how burning fossil fuels contributes to global warming, and for the costs of floods and wildfires that follow.
Russell argued state lawsuits can address damage inside Colorado no matter where the fuels were produced. The local governments point to financial burdens from disasters and seek damages that could reach into the billions.
One disaster looms large in the Colorado story even though it came after the filing. The 2021 Marshall Fire destroyed nearly 1,100 homes, killed two people, and left about $2 billion in damage. It remains the costliest wildfire in state history. Boulder had already sued years earlier.
Justice Elena Kagan cast the climate case as the next chapter in a familiar pattern of state-based mass litigation.
"This is Chapter 3."
She was comparing it to earlier state suits over tobacco and opioids. Shanmugam pushed back hard. "This is a different book," he said. The harms Boulder claims "are diffused nationwide and indeed worldwide," not the kind of localized injury those earlier cases turned on.
Justice Ketanji Brown Jackson floated a narrower exit ramp. She asked why the Court should not wait until state courts finish their work.
"Why shouldn’t we wait and hear all of these claims once the state courts are done?"
That jurisdictional off-ramp would delay a merits ruling. It would not answer whether cities may use tort law to run climate policy.
The conservative-majority Court has already shown wariness toward expansive environmental regulation. In 2022 it limited the EPA's authority to regulate carbon dioxide emissions from power plants. Last month, relative to the arguments, the EPA moved to repeal rules that limit emissions from coal- and natural gas-fired plants. States and cities have already sued over that repeal.
Against that backdrop, Boulder's theory asks justices to green-light a parallel track: state-court damages actions that could pressure the same industries and the same national energy system. Governments in blue-leaning areas have filed a flurry of these cases seeking damages that could total billions. Industry says a Supreme Court win would end most of them.
A decision is expected in the coming months. With Alito recused, a 4-4 split would leave the Colorado high court's go-ahead in force and send Boulder back toward trial. A clear majority for the companies would likely collapse the wider litigation campaign.
Local officials do not get to revise national energy policy by filing tort suits and daring courts to stop them. That job belongs to Congress and the voters, not to a patchwork of city attorneys chasing oil companies for the weather.
