Supreme Court Opens Term With Blockbuster Climate Case

The U.S. Supreme Court opened its new term on Monday with oral arguments in a landmark climate change case that could determine whether states and local governments can hold fossil fuel companies financially accountable for the localized harms of a warming planet. The dispute, Suncor Energy (U.S.A.) Inc. v. County Commissioners of Boulder County, No. 25-170, pits a Colorado community against two of the world’s largest energy companies and carries implications that reach far beyond the climate.

Boulder, Colorado, sued ExxonMobil and Suncor Energy in 2018, alleging the companies knew for decades that fossil fuels harmed the climate but concealed and misrepresented those dangers—costing the community millions in disaster recovery and climate adaptation. As NPR reported, Boulder argues the companies “deceived people about the harms of fossil fuels and contributed to disasters” that have strained local finances.

The case is one of roughly two dozen similar climate accountability suits moving through state courts nationwide. A broad ruling against Boulder could end most of them.

Context: A Case Years in the Making

Boulder’s suit rests on a novel application of state tort law—the same category of public-interest litigation that states and municipalities have used against tobacco companies, opioid manufacturers, and, more recently, technology firms. Rather than seeking to regulate greenhouse gas emissions, Boulder seeks monetary compensation for past and future costs of repairs, emergency services, property damage, and climate adaptation.

According to a Colorado Public Radio analysis, Boulder contends the companies “knew about the risks of burning fossil fuels, but continued to market their products anyway.” A 2018 report prepared for the county estimated Boulder would need to spend between $96 million and $157 million to prepare for just some of its climate impacts—a figure that has since grown.

The legal fight has developed against a broader history of climate tort litigation. In its 2026 primer on the case, the Congressional Research Service traces the genealogy back to American Electric Power v. Connecticut and to Illinois v. City of Milwaukee, cases that alternately recognized and then saw Congress displace a federal common law of interstate pollution. Crucially, the Supreme Court left unresolved whether such suits could proceed under state law rather than federal law—the very question now before the justices.

The Marshall Fire of December 2021, which destroyed more than 1,100 homes in Boulder County, has become a central emblem of the harms at issue. Daryl McCool, a Superior resident who lost her historic 1901 home, described the devastation to NPR: “There’s basically nothing left. A 2,000-degree fire burns everything, like coins were melted, bicycles melted.”

The Two Questions Before the Court

The Court agreed to hear the case on two distinct questions. The first is whether federal law—the Constitution and the Clean Air Act—precludes state-law claims seeking relief for injuries allegedly caused by interstate and international greenhouse gas emissions. The second is whether the Court has the jurisdiction to hear the case at all at this early stage, before any trial or judgment.

The energy companies argue that only the federal government has the power and expertise to address a global problem like climate change, and that allowing Boulder’s suit to proceed would have sweeping consequences. In their briefs, they contend Boulder is attempting to use state law to “impose potentially crushing monetary liability” on energy producers, and that the Clean Air Act—which regulates air pollution—supposedly bars the claims because it assigns emissions regulation to the federal government.

The Trump administration has sided with the companies. In its own brief, the Department of Justice argued Boulder was making a run around the federal government to regulate emissions. “Can one city wield one state’s law to dictate how the rest of the world must address a global problem with global effects?” the government asked, in language quoted by Colorado Public Radio. “The Constitution supplies the answer: Absolutely not.”

Boulder counters that its claims fall well outside the bounds of federal environmental regulation because it targets deceptive marketing and sales practices, not emissions. As the county’s brief puts it, the Clean Air Act “certainly does not charge the EPA with regulating deceptive marketing of fossil fuels.”

Divided Voices, Far-Reaching Stakes

The case has drawn an extraordinary volume of outside participation. According to the SCOTUSblog case docket, nearly 200 members of Congress and more than 40 states signed onto competing amicus briefs. The insurance industry, chambers of commerce, several large tribes, and a coalition of red states lined up behind the companies; seven Colorado ranchers, former EPA administrators, and a coalition of states and cities—including New York City—supported Boulder.

The rhetoric has sometimes been sharp. Todd Zywicki, a law professor at George Mason University who filed a brief supporting the companies, told Colorado Public Radio that the case was about whether “a bunch of one-percenter hippies in Boulder County” should be allowed to dictate energy policy. Corey Riday-White of the Center for Climate Integrity framed the matter differently, arguing that if a corporation “know[s] you are going to cause harm, and you don’t tell someone, then you should help clean up that harm.”

The stakes extend well beyond climate law. As appellate attorney Deepak Gupta noted, the Court’s ruling could reshape liability rules for “[p]ollution by forever chemicals, nuisance suits over AI data centers, [and] opioids litigation—all of these are about the local effects of conduct that runs across borders.” UCLA environmental law professor Alejandro Camacho warned that a broad ruling against the county “ends essentially all of them”—the two dozen pending climate suits—and could also affect climate “Superfund” laws enacted in Vermont and New York.

A Last-Minute Recusal

On the eve of the argument, the Court notified lawyers that Justice Samuel Alito would not participate in the case, a decision the Court did not explain but which followed sustained calls for his recusal because of his investments in Phillips 66 and ConocoPhillips. “The public should not have to wonder whether a justice’s personal investments could benefit from a ruling that shields the fossil-fuel industry from liability,” Justin Kloczko of Consumer Watchdog told NPR.

With eight justices hearing the case, a 4-4 tie would leave the Colorado Supreme Court’s decision allowing Boulder’s suit to proceed in place.

What to Watch

The Court could resolve the case in several ways. It might uphold the Colorado Supreme Court’s ruling and let the case proceed; it might dismiss the appeal as improvidently granted on jurisdictional grounds, which would also allow Boulder’s suit to advance; or it could rule broadly on the merits and potentially foreclose similar actions across the country.

Legal observers remain uncertain how the conservative supermajority will draw the lines. As Financial Post noted, the case represents a pivotal test of how far courts will allow state and local governments to reach in policing corporate conduct with global consequences.

For the residents of Boulder County, the outcome carries a more immediate meaning. Louie Delaware, who lost his home in the Marshall Fire and planned to attend Monday’s arguments, put the question simply: “You know it’s our responsibility to leave things better for the next generation. And the way we’re going right now is counter to what that’s been in the past.”

A decision is expected by the end of the term.