Justices pressed both sides Monday as the U.S. Supreme Court heard Boulder's climate lawsuit against ExxonMobil and Suncor Energy, probing federal authority and whether the appeal reached them too soon. No ruling came from the bench, and none is likely for months.
At issue in No. 25-170 is whether federal law bars the City of Boulder and Boulder County from collecting damages under Colorado law for harm they tie to interstate and international greenhouse gas emissions. The Court added its own question about whether it has jurisdiction to hear the appeal at all, as the case docket shows. Whatever the outcome, these arguments will not settle whether the companies caused Boulder's injuries or owe it money.
Chief Justice Roberts Asked About Lawsuits in Every State
Only eight justices took part, since Justice Samuel Alito withdrew on September 28 without explanation. Chief Justice John Roberts wanted to know how things would work "on the ground" if municipalities in every state brought similar suits. Arguing for the United States on the companies' side, Principal Deputy Solicitor General Sarah Harris told the Court that Boulder's claims "egregiously" exceed what a state can do. The government had laid out that position in a July motion citing constitutional limits on state power and federal control of foreign affairs.
The companies drew hard questions too. Justice Elena Kagan asked where the text supporting their federalism argument could be found, according to a statement from the Center for Climate Integrity, an advocacy group that backs the lawsuits. In the group's account, Justice Amy Coney Barrett called the preemption argument "a little slippery." Justice Ketanji Brown Jackson remarked that the case is still at a very early stage.
A Jurisdiction Ruling Could Return the Case to Colorado
Jackson's point goes to the off-ramp. Boulder argues that the Colorado Supreme Court's May 2025 decision letting its claims proceed was not a final judgment and cannot be reviewed yet, while the companies say it can, as Beveridge & Diamond explains. If a majority agrees with Boulder, the case goes back to Colorado with no word on preemption. An even split among the eight would leave the Colorado ruling standing, again without a national precedent.
Boulder sued in April 2018, alleging the companies hid what they knew about the climate dangers of fossil fuels. Its city government links the claims to local costs from heat, wildfire, drought and poor air quality, through counts of nuisance, trespass, unjust enrichment and civil conspiracy that remain unproven. Even a win in Washington would only move the city closer to a trial, so local adaptation projects will keep competing for money through ordinary capital budget tradeoffs.
Companies with exposure to similar suits will read the opinion closely for its reach, expected by the end of the term in late June. A narrow ruling on jurisdiction leaves dozens of cases moving on their current tracks and keeps feeding litigation assumptions in earnings forecasts. A broad ruling on preemption, in either direction, would reset that math and the uneven compliance exposure it creates.
