Supreme Court's conservative wing signals skepticism toward Boulder's climate suit against Exxon and Suncor

The Supreme Court opened its 2026-27 term Monday morning with a two-hour argument that put the future of some three dozen state and local climate lawsuits in the balance. Eight justices took the bench in Suncor Energy v. County Commissioners of Boulder County, and by the time arguments closed, the court's conservative bloc appeared broadly inclined to side with the oil companies.

The case began in 2018. The city and county of Boulder sued ExxonMobil and Suncor Energy, alleging the companies had lied about the dangers of burning fossil fuels and left taxpayers to foot the bill for floods, wildfires, drought and more. The companies and the Trump administration spent Monday asking the justices to end it before it ever reaches a jury.

Eight of the court's nine justices heard nearly two hours of oral arguments in the case. Justice Samuel Alito recused himself from the case, opening the door to a possible 4-to-4 split, which would leave the Colorado Supreme Court's ruling for Boulder in place without setting binding precedent.

What Boulder is asking for

The question before the court is whether the city and county of Boulder can sue energy companies under state law to recover monetary compensation for harms attributable to climate change. Boulder's attorneys argued the suit is a straightforward state-tort fraud claim. On the merits, Boulder contends its suit is a constitutionally permissible exercise of state police power to regulate deceptive marketing and sales practices. Because the Clean Air Act addresses neither marketing nor sales, Boulder argues the act does not preempt its claims.

Some three dozen local governments and states throughout the United States have filed similar lawsuits in state court against fossil fuel companies over their alleged deception and false advertising. The scope of those suits gave the oil companies their strongest rhetorical weapon on Monday. Kannon Shanmugam, arguing for Suncor and ExxonMobil, told the justices the case "involves an unprecedented effort to use state law to regulate global conduct." "If Boulder's claims are allowed to go forward," he said, "some 90,000 municipalities across the country will have the ability to make national and international energy policy by asking juries to impose catastrophic damages on selected fossil fuel producers."

The Trump administration, aligned with oil

The Trump administration is backing ExxonMobil and Suncor in the case. Sarah Harris, the principal deputy solicitor general, argued the federal government's position from the lectern. Boulder's lawsuit, Harris said, "egregiously exceeds" constitutional limits of state authority. "Interstate air pollution is an inherently federal area, and Congress hasn't authorized this suit in the Clean Air Act," she said.

That framing got a receptive hearing from Justice Brett Kavanaugh. Kavanaugh repeatedly said that four of the Supreme Court's decisions dating back to 1972 make clear that interstate air and water pollution are matters of federal law. Those arguments seemed to gain traction with other conservative justices as well, including Kavanaugh, who questioned why prior court cases had not already shut the door on Boulder's claims.

The liberal wing pushed back hard. Justice Elena Kagan compared Boulder's suit to the lawsuits state and local governments brought against tobacco companies in the 1990s and the more recent opioid litigation, which she said accused companies of misrepresentations that led people to overuse their products. Kagan questioned the companies' claim that states surrendered the power to regulate interstate pollution when they joined the union. "Where is the text for that? Where's the support for that? Where's the precedent for that? Where's the anything for that?" she asked.

Justice Amy Coney Barrett, a potential deciding vote, asked the attorney representing Boulder County, Kevin Russell, to explain why a state may not pass a law "purporting to cap emissions in the other 49 states" but "the same thing can happen through the tort suit." That question put Barrett in ambiguous territory: it tested Boulder's position, but it did not commit her to the oil companies' framing either.

The jurisdiction problem

Before any merits question, the justices spent significant time on whether the court has jurisdiction to hear the case at all. At oral argument, Justice Clarence Thomas raised the jurisdiction issue at the outset in his questioning of both Suncor's and the government's counsel. Justices Elena Kagan, Sonia Sotomayor and Ketanji Brown Jackson returned to jurisdiction repeatedly, particularly in questioning Suncor's counsel.

Boulder argues that Suncor and ExxonMobil lack standing to challenge Boulder's suit, which has not yet proceeded to trial and has not yet inflicted any legally cognizable harm. Boulder also contests the Supreme Court's statutory jurisdiction to hear this case, arguing that there is no final state-court judgment for the court to review.

If the court splits 4-to-4, the Colorado Supreme Court's ruling for Boulder would stand in place, without setting binding precedent for any of the dozens of similar suits pending in state courts across the country. That outcome would let the cases proceed but give no definitive answer to the federal preemption question.

What the lower courts said

The Colorado Supreme Court affirmed the lower court's preemption order in a 5-to-2 vote, rejecting the oil companies' argument that federal law blocked Boulder's claims. On February 23, 2026, the U.S. Supreme Court granted review. The court also posed a question to the parties of whether it had statutory or constitutional authority to hear the case at all.

Monday's argument offered few clear signals about how the court will rule, but it revealed where the fault lines lie. The court's three liberal justices appeared more supportive of Boulder, while the questions from Chief Justice John Roberts and Justice Kavanaugh seemed to favor the energy companies.

Stakes beyond Boulder

A ruling for the oil companies would, in practice, extinguish nearly every pending climate-liability suit filed by state and local governments. A ruling for Boulder would send the case back to Colorado state court for trial. Neither result is imminent. The case is set to be argued during the Supreme Court's October 2026 term, with a decision expected by mid-2027.

All three Boulder County commissioners were in the courtroom for the argument, according to Colorado Public Radio. Outside the court, environmental advocates and survivors of Colorado's 2021 Marshall fire rallied on the plaza as arguments ran inside.

The Senate, meanwhile, passed its own piece of energy-adjacent legislation last week. In a large, bipartisan 77-22 vote, the Senate passed the Protect College Sports Act of 2026 (S. 4668). That bill now heads to a House that is not expected back in session until November 9, after the midterms.

What to Watch

• Alito's recusal and the 4-4 math. Justice Alito's recusal from the case opens the door to a possible 4-4 split, which would leave the Colorado Supreme Court's ruling for Boulder in place without setting binding precedent. Watch for any reporting on why Alito stepped aside; a financial conflict is the most common explanation but has not been publicly confirmed.
• Barrett as the swing. She challenged both sides Monday. Her final vote could determine whether the case proceeds or whether the court shuts the courthouse door on all similar climate suits. Legal analysts at Just Security flagged her line of questioning as the argument's most unpredictable thread.
• The jurisdictional off-ramp. If a majority finds the court lacks jurisdiction, the justices could dismiss without deciding preemption, leaving the climate-liability question for another day and another case.
• Copycat suits in 35-plus jurisdictions. Some three dozen local governments and states throughout the United States have filed similar lawsuits in state court against fossil fuel companies. Their lawyers are reading this argument closely. A decision expected by June 2027 would land squarely in midterm-election general season, when energy policy is already a top voter concern.

Sources: CBS News | Colorado Public Radio | Just Security | Colorado Newsline | Daily Caller | Legal Planet | Harvard EELP | Wikipedia case history | City of Boulder | SCOTUSblog