Title: Supreme Court's Biggest Climate Case in Years Opens Monday: Thomas Could Be the Deciding Vote
The first case of the U.S. Supreme Court's fall 2026 term will be the most significant climate lawsuit in nearly two decades: the City of Boulder and Boulder County, Colorado, suing ExxonMobil and Suncor Energy for climate-related damages. Oral arguments are set for Monday, October 5, at 10 a.m. ET. The central question is not climate science but jurisdiction: can states and cities sue oil companies in state court? And Justice Clarence Thomas — long a reliable vote against environmentalists — has unexpectedly become the swing vote they are counting on.
Thomas Emerges as the "Justice to Watch" Thomas is the longest-serving current justice and one of the court's most stalwart conservatives, his views on guns, race, and religion rarely in doubt. But in this case, environmentalists aren't writing him off: in recent years he has staked out positions skeptical of letting federal law trump state law, particularly when Congress has not clearly stated its intention. Boulder's lawyers quoted Thomas and Justice Neil Gorsuch six times in written arguments filed over the summer. "The justices to watch here are very much Justice Gorsuch and Justice Thomas," appellate attorney Deepak Gupta said at a recent event hosted by the Supreme Court Institute at Georgetown Law Center. "I think they will find the lack of any textual hook for these arguments troubling."
Alito's Recusal Opens the Door to a 4–4 Tie Fellow conservative Justice Samuel Alito recused himself on September 28 without explanation. His 2025 financial disclosure shows holdings in energy companies facing similar climate lawsuits nationwide, including up to $15,000 in ConocoPhillips and between $15,001 and $50,000 in Phillips 66. With Alito out, only eight justices will hear the case — raising the possibility of a 4–4 tie, which would affirm the Colorado Supreme Court's May 2025 ruling that the case may proceed in state court.
The Core Question: Can State Courts Hear the Case? Boulder sued in 2018, alleging the companies knowingly contributed to harmful climate alteration while concealing the dangers of their products and misleading the public, and seeking damages for wildfires, flooding, extreme heat, and drought. The oil companies argue the Clean Air Act and federal authority over greenhouse gases preempt state-law nuisance claims. The Trump administration is siding with the oil companies. Notably, federal judges recently struck down New York's 2024 climate "superfund" law as preempted by the Clean Air Act, with similar challenges facing Vermont's law.
What's at Stake: Dozens of Lawsuits Hang in the Balance About 40 local governments have filed similar suits, and this ruling will decide their fate. "Justices Thomas and Gorsuch have both written opinions that firmly reject the idea that federal law can shove state law out of the way based on hazy arguments about a law's intentions or policy consequences," said Kirti Datla, director of strategic legal advocacy at Earthjustice, which filed a brief opposing Suncor and Exxon — "that's what Suncor's arguments boil down to in this case." A watchdog found that 25 of the 38 amicus briefs supporting Exxon and Suncor were written by groups with financial ties to the fossil fuel industry. Boulder has also picked up surprising allies: Colorado ranchers and some conservative legal scholars back its right to sue.
What to watch next: oral arguments stream live Monday at 10 a.m. ET, with a written opinion expected months later. A 4–4 tie would let Boulder's case proceed in state court — and put the oil giants before a jury.