Supreme Court justices send mixed signals as Boulder climate case reaches argument

The U.S. Supreme Court heard arguments on Oct. 5 in a case that will help decide whether cities, counties and states can sue oil companies in state court over climate damages. Colorado Public Radio reported that the justices spent the session probing whether federal law blocks such suits, and accounts of how the argument went differ.

The case, Suncor Energy v. County Commissioners of Boulder County, began in 2018, when the city and county of Boulder sued ExxonMobil and Suncor Energy. According to Inside Climate News, the suit alleges a decades-long campaign of deception by the companies about the climate risks of their products. Boulder seeks money to cover the costs of adapting to local effects such as extreme heat and wildfires. The Colorado Supreme Court allowed the case to move toward trial in 2025, and the companies appealed.

The questions before the court

The justices agreed to decide two questions. The first is whether federal law precludes state-law claims for injuries allegedly caused by the effects of interstate and international greenhouse gas emissions on the global climate. The second is whether the court has statutory and Article III jurisdiction to hear the case at all.

Justice Samuel Alito recused himself without explanation, CBS News reported. His 2025 financial disclosures listed holdings in ConocoPhillips and Phillips 66, but not in Exxon or Suncor. With eight justices participating, a 4-4 split would leave the Colorado ruling in place, according to CBS.

What the lawyers argued

Kannon Shanmugam, who represented the oil companies, told the justices that allowing Boulder’s claims to proceed would give about 90,000 municipalities across the country the ability to set national and international energy policy by asking juries to impose large damages on selected fossil fuel producers, CPR reported. He described the suit as an unprecedented effort to regulate global conduct through state law, according to CBS.

Kevin Russell, representing Boulder, said the lawsuit is not an effort to reduce emissions. He told the court it asks the companies to pay for part of the damage their activities cause, CPR reported. He also argued that states have historically had the power to provide tort remedies for injuries within their borders, according to CBS.

Sarah Harris, arguing for the Trump administration, said the suit goes well beyond the limits the Constitution places on state authority, CBS reported. The Department of Justice had earlier filed a brief supporting the oil companies, Inside Climate News reported.

Differing accounts of the bench

Democracy Now reported that the justices appeared skeptical of claims that federal law preempts state tort law. Other coverage described the questioning as more mixed.

Stanford Law School’s analysis of the argument by Molly Loughney Melius, executive director of its Environmental and Natural Resources Law and Policy Program, recorded several lines of questioning. Justice Elena Kagan compared the case to earlier tobacco and opioid litigation, calling it “chapter three,” according to CBS. Justice Brett Kavanaugh focused on the argument that regulating emissions that cross state lines is inherently a federal matter. Justice Neil Gorsuch asked whether, if federal regulators step back, no one could sue at all.

Justices Clarence Thomas and Ketanji Brown Jackson raised concerns that the case may be premature, which could give the court a procedural way out, according to the Stanford analysis. Jackson said the discussion made her think the case was early and that the court’s exercise of jurisdiction may be premature, CPR reported.

Beyond Boulder

More than two dozen climate liability suits are pending against fossil fuel companies across the country, and none has reached trial, according to Inside Climate News. Melius wrote that if the court does not let Boulder’s case go to trial, its reasoning could shield other industries, from Big Tech to Big Pharma.

Alina Miranda, 16, whose home was destroyed in Colorado’s Marshall Fire, signed a friend-of-the-court brief urging the justices not to take away local governments’ ability to hold corporations accountable, Democracy Now reported.

CBS News reported that a decision is expected by summer 2027.