On February 23, 2026, the U.S. Supreme Court agreed to hear arguments in the City and County of Boulder’s climate lawsuit against two major energy companies. This offers the first real opportunity to rein in the nationally-coordinated climate litigation campaign that has sought to force policy outcomes through the courts that elected officials and voters have repeatedly rejected.
Here’s what you need to know. This post will be regularly updated.
What is the Boulder climate lawsuit?
In 2018, the City and County of Boulder and San Miguel County filed a public nuisance climate lawsuit against Exxon Mobil and Suncor, seeking financial damages to pay for the costs of climate change. From the outset, the case raised serious questions about whether local governments should be allowed to use state tort law to extract damages for global phenomena driven by worldwide greenhouse gas emissions that have occurred across decades, across borders, and with the full knowledge and legal sanction of federal and state governments.
After San Miguel’s case was separated from Boulder’s in 2021, Boulder spent five years fighting jurisdictional battles – all the way to SCOTUS and back – before finally getting a May 2025 Colorado Supreme Court ruling allowing the case to proceed towards discovery and trial.
The companies appealed, and in February 2026, the U.S. Supreme Court agreed to take up the case.
What questions will the Supreme Court consider and what do they mean?
The Court will hear arguments on two separate questions – one that goes to the heart of the entire campaign, and one that could let the justices sidestep it.
The big one: can state law be used to sue energy companies for the effects of international greenhouse gas emissions on global climate change? This is what the climate litigation campaign has always really been about: using tort law as a backdoor emissions regulator, extracting damages that function as a de facto carbon tax that Congress never voted for and voters never approved.
The companies argue that federal law forecloses exactly this kind of state-law end-run, and that issues of greenhouse gas emissions, interstate commerce, national energy policy, and foreign affairs belong at the federal level — not in a patchwork of state courtrooms where judges can impose wildly inconsistent liability on American energy producers.
The second question – added by the Court at Boulder’s urging – asks whether SCOTUS even has jurisdiction to hear the case right now. If the justices rule narrowly on procedure, the broader preemption question stays unresolved and Boulder’s case will continue in state court.
When will the court hear arguments?
Arguments are expected during the October 2026 term, with a decision anticipated in winter 2026 or spring 2027.
What is the likely impact?
This case has nearly three dozen copycats waiting in the wings. Defendants in similar lawsuits across the country are already moving to pause proceedings – several cases, including a homeowner class action in Washington, have been stayed pending SCOTUS’s decision. Others, in Chicago and Washington state have filed similar motions.
If the Court rules broadly for the energy companies — holding that state law cannot be used to impose liability for global and interstate emissions — it would deal a major blow to the entire national climate litigation campaign, as plaintiffs across the country have sought to use state tort law and to have their cases heard in state court.
That would be an appropriate outcome. Allowing dozens of state and municipal governments to impose state-court liability for inherently global phenomena would fragment national energy policy, chill domestic energy production, and circumvent the democratic process by substituting courtroom judgments for legislative ones.
If the justices punt using the jurisdictional question, Boulder’s case would return to state court, but the underlying legal vulnerabilities of the case would remain.
Where do Colorado leaders stand on the case?
The response to the filing of the lawsuit was met immediately with strong opposition from Colorado state leaders, including the Denver Post editorial board and former Secretary of the Interior Gale Norton, who also served as Colorado’s Attorney General.
Then-governor John Hickenlooper and one his top administration officials warned that litigation was not the best way to pursue an environmental agenda. Hickenlooper’s predecessor, current Governor Jared Polis, also didn’t support the case and remained silent on the issue throughout his entire time in office.
Conservation Colorado, a leading environmental group in the state, also declined to publicly support the lawsuit and The Denver Post editorial board delivered a sharp rebuke to the lawsuit, writing:
“Without fossil fuels, transportation would stagger to a halt, agricultural productivity would plummet, millions would suffer from cold, heat and hunger, and untold legions would suffer premature death. That’s why any comparison between fossil fuel companies and the tobacco industry, whose product is a health disaster with no redeeming economic value, is so wide of the mark…”
Who did Boulder hire as outside counsel?
Boulder’s attorneys have admitted that their true goals for the litigation aren’t financial damages, but rather achieving preferred public policy outcomes.
A lead attorney for EarthRights International, a nonprofit representing Boulder, said that a key goal of the lawsuit is “to raise the price of the products” like oil and gas to shift the behaviors of companies and consumers. Another attorney long involved with the case, David Bookbinder, was even more direct last year, calling the lawsuit an “indirect carbon tax.”
Officials with the Boulder City Council also undercut their own legal arguments by publicly stating their true goal was achieving political and public policy objectives. In 2021, a memo prepared for a study session outlined the goal of “systems-level change”:
“Boulder has also been a national leader in exploring the use of the legal system in pushing for larger systems-level change. Both through its active participation in multi-jurisdiction efforts — like the Clean Power Plan Plaintiffs group — or its climate liability lawsuit with Boulder and San Miguel Counties against ExxonMobil and Suncor, Boulder has demonstrated that there are a range of different levers cities can take hold of to drive more fundamental systems change.” (emphasis added)
Why did the Supreme Court agree to hear the case this time?
Earlier petitions in similar cases, including Honolulu, never made it past the cert stage. This time, several things changed:
The biggest: the Department of Justice proactively weighed in to explain why the Court should take the case – a reversal from the Honolulu petition, whether the Solicitor General argued against review.
Beyond that, the legal landscape has shifted. Since the Honolulu petition was rejected, ten other cases have been thrown out or withdrawn, while two cases have been allowed to proceed – widening the split among state courts that warrants Supreme Court resolution.
Add in the fact that the Colorado Supreme Court’s ruling constitutes a final decision, the companies argue, giving the Supreme Court jurisdictional footing to review it.
Does the EPA’s ruling on the Endangerment Finding impact climate lawsuits?
The EPA has maintained the Clean Air Act will continue to preempt state common law claims and statues that try to regulate out-of-state emissions.
As West Virginia’s Solicitor General, Michael Williams, explained:
“Before the Clean Air Act was a twinkle in Nixon’s eye, there was this whole existing body of federal common law that said interstate emissions issues really are issues for the federal government…Ultimately, I think that if you pull the Clean Air Act back, you’re still left with that original preexisting body of federal common law. It’s going to have the same preemptive force that it did before the Clean Air Act ever came to be.”
Some legal observers have noted that revoking the Endangerment Finding could actually help companies in these climate lawsuits. In the case of Boulder, the Colorado Supreme Court rejected defendants’ argument in part because of the Clean Air Act, there’s no federal common law and no preemptions. Without the endangerment finding, there’s a possibility that federal common law could be used in the defendants’ preemption argument.
However, the Endangerment Finding will not go into effect until April 20, 2026 and could change pending legal challenges.
