Supreme Court to review energy companies’ attempt to end Boulder climate change lawsuit

Washington- When the Supreme Court returns to sit on Monday for the first time since late June, it will begin its new term with a major case involving an effort by the city and county of Boulder, Coloradoto hold fossil fuel producers accountable for the impacts of global climate change.

The Boulder lawsuit is one of dozens filed by state and local governments against energy companies in state courts seeking damages for past and future harm they say is caused by the buildup of greenhouse gases in the atmosphere, which has led to global warming.

The long-running dispute brought by Boulder targets Exxon Mobil, the nation’s largest energy company, and Suncor Energy, which operates two oil refineries in Colorado. The trial is in its early stages and the question before the Supreme Court is whether the trial can proceed or is barred by federal law. A victory for Boulder at the Supreme Court would not mean it will ultimately prevail against fossil fuel producers in state courts.

“This is not a judgment on whether these cases succeed. This is a judgment on whether people can make their case,” said Jonathan Adler, a law professor at William & Mary who has written on federalism and environmental law and filed a friend-of-the-court brief in favor of Boulder. “And even if they succeed in making their case, the scope of what they can pursue may well be reduced and may well be significantly reduced.”

Boulder’s lawsuit dates back to 2018. Filed in state court, the city and county allege that Exxon and Suncor’s conduct has caused or contributed to climate change, which has forced Boulder to face extreme heat, larger and more frequent wildfires and damage to the ecosystem, among other problems.

Boulder officials raised five claims under state law. They claim that the production and allegedly deceptive marketing of fossil fuels by energy companies has led to “uncontrolled” use of their products, which has caused a rapid increase in the concentration of greenhouse gases in the atmosphere.

Exxon and Suncor attempted to take the case to Federal Court, but were unsuccessful. The companies also asked the Boulder County District Court to dismiss the case on the grounds that federal law barred claims against them. When the state court denied that request, the companies asked the Colorado Supreme Court to intervene.

The state high court ruled in favor of the city and county of Boulder, and Suncor and Exxon appealed to the U.S. Supreme Court.

In addition to considering whether federal law precludes Boulder’s claims from state law, the Supreme Court asked attorneys for both sides to determine whether it has jurisdiction to review the Colorado Supreme Court’s decision.

Only eight of the nine justices will participate in Monday’s arguments, with the Supreme Court saying last week that Justice Samuel Alito had chosen to recuse oneself of the case. No reason was given for Alito’s decision. His financial disclosures for 2025 show he held individual stakes in two energy companies, ConocoPhillips and Phillips 66. He reported no individual shares in Exxon or Suncor.

Alito’s absence leaves open the possibility that the Supreme Court will split 4-4 in the case. If that happens, the decision of the lower court – the Colorado Supreme Court, in this case – would stand.

A “national problem”

Lawyers for Exxon and Suncor argued before the Supreme Court that the Constitution and the Clean Air Act preclude claims seeking to remedy harm caused by interstate greenhouse gas emissions. The Clean Air Act, they said, did not invite state law to apply to disputes involving interstate pollution.

If the Colorado Supreme Court’s decision is upheld, “it would authorize our nation’s fifty states, tens of thousands of municipalities, and even hundreds of millions of individuals to ask local courts to establish countless conflicting climate policies for the nation,” lawyers for Exxon and Suncor argued.

Additionally, energy companies and the Trump administration, which supports Exxon and Suncor in the matter, have warned that efforts like Boulder’s to achieve reductions in the effects of greenhouse gas emissions — including those released abroad — undermine the government’s control over foreign affairs.

“Such lawsuits would bypass existing U.S. diplomatic avenues to combat climate change in favor of countless state legal avenues,” lawyers for Exxon and Suncor said. “And imposing potentially devastating liability on fossil fuel producers will undermine the government’s quest for primacy in global energy production.”

Because greenhouse gases emitted from sources in every state and around the world cannot be mixed or traced, the companies warned that allowing all 50 states to enforce their own laws would lead to confusion. Only a “neutral, uniform federal law” can resolve disputes over air and water regulations, they said.

“This is a national problem, so it requires a national solution,” Michael Williams, West Virginia’s attorney general, told reporters at a press briefing Wednesday.

West Virginia and 25 other states support Suncor and Exxon Mobil and argue that the Boulder lawsuit undermines their ability to achieve their own policy goals on energy production and environmental protection.

“We don’t dispute the idea that a state can actually regulate sources of supply within its own borders. So if West Virginia wants to regulate a coal plant in West Virginia, we assert the right to do so,” Williams said. “Similarly, if Colorado wants to regulate emissions coming from Colorado to Colorado, it’s free to do that as well. What it’s not free to do is say, hey, you transmitters, anywhere in the world…we’re going to charge you money for any of these emissions anywhere in the world.”

But Boulder lawyers urged the Supreme Court to reject the appeal on the grounds that it lacks jurisdiction. If the justices choose not to do so, they said the Colorado Supreme Court’s decision should be upheld.

“Is there anything implicit in the Constitution that prohibits this prosecution?” they wrote in a file. “Nothing helps.”

Boulder noted that there is often litigation to address the local impacts of problems that could benefit from international solutions, such as food contamination, human trafficking and the fentanyl crisis. The city and county’s efforts to hold energy companies accountable are just another example, they said.

“Nor does the fact that climate change is a global problem prevent states from repairing its local damages,” they wrote in a paper. “This litigation is not an attempt to solve climate change; it simply requests that petitioners bear their fair share of local costs incurred in part as a result of their tortious conduct.”

Boulder also pushed back on the energy companies’ argument that the Clean Air Act preempts its claims, and said the law governs emissions, not the conduct of upstream fossil fuel producers. Additionally, attorneys for the city and county said they did not sue over emissions, but over allegedly deceptive marketing and production, which the Clean Air Act does not regulate.

“Indeed, avoiding liability would not require reducing emissions at all – it would only be necessary to tell the truth, so that the public can make informed consumer decisions, without the distorting effect of the petitioners’ false claims,” they said.

The Trump administration says Boulder’s lawsuit is causing “unnecessary diplomatic friction” with foreign countries where Exxon and Suncor produce and sell their fossil fuels. But Adler, the William & Mary professor, noted that the Trump administration has withdrawn from international agreements who seek to combat global warming and greenhouse gas emissions.

The foreign affairs argument “seems to suggest that any time the executive branch says it wants to negotiate in a space where companies could be held liable for damages to which they may have contributed, that would really give the executive branch the opportunity to preempt any type of litigation it wants. That can’t be the law,” he said. “If there was a real conflict between an actual treaty, of course that could trump state law. But we don’t even have that.”

Adler also said Congress could step in and restrict lawsuits against fossil fuel companies for damages related to their products. In fact, he took similar steps in 2005 when lawmakers passed a federal law that protects gun manufacturers civil suits aimed at holding them responsible for harm resulting from the criminal use of their firearms.

“If Congress believes that what’s happening here is a combination of plaintiffs’ lawyers and activists trying to make energy less available or less affordable, or otherwise create pressure on fossil fuel companies, Congress has the tools to do something about it,” he said. “That’s a matter for the legislature, not the courts.”

A decision from the Supreme Court is expected by summer 2027.