The Supreme Court appeared sharply divided Monday over whether Boulder, Colorado, may pursue state-law claims seeking climate-related damages from ExxonMobil and Suncor, with justices debating whether the case is fundamentally about consumer deception or interstate pollution governed by federal law.
By yourNEWS Media Newsroom.
WASHINGTON — Supreme Court justices wrestled Monday with whether Boulder, Colorado, can use state law to seek damages from ExxonMobil and Suncor Energy over alleged climate-related harms, in a case that could affect dozens of similar lawsuits filed by state and local governments around the country.
With Justice Samuel Alito recused, eight justices heard arguments in Suncor Energy v. County Commissioners of Boulder County, a dispute centered on whether Boulder’s claims are traditional state-law tort actions involving alleged deception or an attempt to regulate interstate and global greenhouse gas emissions through local courts.
The two sides offered sharply different descriptions of the case.
Kannon Shanmugam, representing ExxonMobil and Suncor, told the court that Boulder’s lawsuit “involves an unprecedented effort to use state law to regulate global conduct.”
“If Boulder’s claims are allowed to go forward, 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,” Shanmugam said during oral arguments.
The companies told the court that nearly 60 state and local governments have brought similar climate-related cases, according to reporting on the litigation.
Boulder County and the city of Boulder sued Exxon and Suncor in 2018, alleging the companies misled the public for years about the effects of fossil fuels on the climate while continuing to market and sell their products.
The plaintiffs are seeking compensation for costs they attribute to climate change, including infrastructure repairs, environmental damage, emergency preparedness and public-health impacts.
The Colorado Supreme Court allowed the lawsuit to proceed in a 5-2 ruling in May 2025, leading the companies to appeal to the U.S. Supreme Court.
Monday’s arguments revealed disagreement among the justices over both the substance of the dispute and whether the high court should be deciding it at this stage.
Justice Brett Kavanaugh emphasized a line of Supreme Court precedents holding that interstate pollution generally falls under federal law.
“There’s a lot of constitutional theory being tossed around, but we have four precedents on point,” Kavanaugh said.
He cited the court’s Milwaukee pollution cases, International Paper Co. v. Ouellette and American Electric Power Co. v. Connecticut, saying those decisions “make crystal clear that interstate air and water pollution are matters for federal law unless Congress specifically preserves state law.”
Kavanaugh later told Boulder’s lawyer that the court has “a wall of precedent that says state tort law does not apply” to interstate pollution, except in cases relying on the law of the state where pollution originates.
If the court were now to require Congress to expressly block lawsuits like Boulder’s, Kavanaugh said, “this court would be rightly accused of misleading Congress for decades on what the state of the law was.”
Justice Elena Kagan took a different approach, comparing Boulder’s theory to litigation brought against tobacco companies in the 1990s and, more recently, opioid manufacturers and distributors.
Those cases frequently alleged that companies misrepresented the risks associated with their products, causing widespread public harm.
“This is Chapter Three. So, if this is Chapter Three, were Chapters One and Two also preempted?” Kagan asked.
She also challenged the companies’ broader constitutional claim that states surrendered authority over interstate pollution when they entered 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?” Kagan asked.
Justice Amy Coney Barrett, whose questions attracted particular attention because only eight justices are participating, pressed the companies on their reading of the Clean Air Act.
Shanmugam argued that the statute’s saving clause preserves only limited categories of state-law claims.
“Well, I mean, it doesn’t say authorize; it says preserve, and a saving clause suggests that you’re saving something that already exists,” Barrett responded.
Later, Barrett called one of Shanmugam’s answers “a little slippery,” saying that when questioned about federal common law he appeared to be “reverting to the constitutional structure equal sovereignty point.”
Her questioning did not necessarily indicate how she will ultimately vote. Justices frequently test both sides’ positions aggressively during oral arguments.
Justice Sonia Sotomayor was similarly skeptical of the companies’ preemption theory.
“You don’t win unless you get us to say that federal law preempts state law in this area,” Sotomayor told Shanmugam.
Shanmugam agreed.
Sotomayor noted that the court previously allowed some state-law nuisance claims to proceed under the Clean Water Act and questioned why the Clean Air Act should produce a different result.
She also questioned whether the Supreme Court has jurisdiction to decide the dispute at this point.
“Shouldn’t we be certifying this question to the Colorado court instead of us deciding it?” Sotomayor asked. “We have to be sure of our jurisdiction before we take it.”
Justice Ketanji Brown Jackson raised a similar concern, saying the arguments suggested “we’re really early in this case.”
Jackson questioned whether the Supreme Court was stepping in before state courts had fully addressed the federal defenses raised by Exxon and Suncor.
The Trump administration appeared in support of the companies after the court granted the solicitor general permission to participate, according to the Supreme Court docket.
Principal Deputy Solicitor General Sarah Harris told the justices that Boulder’s lawsuit “egregiously exceeds constitutional limits on state authority.”
The administration argues that federal law precludes state and local governments from using tort lawsuits to impose liability over global greenhouse gas emissions.
Justice Neil Gorsuch focused on a potential consequence of that position.
He noted that the Environmental Protection Agency has disclaimed certain regulatory authority over greenhouse gas emissions from motor vehicles and, more recently, stationary sources.
Gorsuch asked whether the administration’s legal theory meant that “because of the Clean Air Act and Congress not addressing this issue, nobody can sue at all.”
“Again, I think that’s correct,” Harris said, pointing to the Clean Air Act’s renewable fuel program as one example of Congress specifically addressing greenhouse gas emissions.
Jackson challenged the procedural path of the companies’ argument.
She told Harris it “feels to me like the defendants in this case are coming in after attempting to remove this to federal court” and are now “coming up with theories that are bringing it back to federal court before the state courts have really had a chance to sort out” the underlying facts.
Kevin Russell argued on behalf of Boulder County and the city of Boulder, according to the city’s description of the case.
“Since the founding, states have had the power to provide tort remedies for injuries occurring within their borders, even when the conduct causing those injuries occurred elsewhere,” Russell told the court.
He repeatedly argued that Boulder is not attempting to regulate emissions directly.
Instead, the city and county say their claims focus on alleged deception by fossil fuel producers and the resulting costs imposed locally.
Kavanaugh challenged that distinction.
Russell said, “this case is not about emissions; it’s about deception and producers.”
Under Boulder’s theory, he added, the companies “can continue to produce as much fossil fuels as they like” provided that consumers are properly informed about the consequences.
Kavanaugh was unconvinced that the distinction necessarily resolves the federalism issue.
Barrett tested the limits of Boulder’s position by asking whether Colorado could pass a statute “purporting to cap emissions in the other 49 states.”
Russell said it could not.
A state-law tort claim is different, he argued, because it does not prohibit conduct elsewhere but instead “requires them to internalize a portion of the costs of their activities.”
Russell acknowledged that Boulder’s theory could potentially extend beyond producers themselves.
Asked whether large retailers of fossil fuels could face similar suits if Boulder prevails, he responded, “Nothing in our theory prevents that.”
He said constitutional doctrines involving personal jurisdiction, choice of law and the dormant Commerce Clause would still impose limits on state litigation.
Russell also pointed to longstanding asbestos and product-liability litigation as evidence that courts are capable of handling large numbers of cases involving common products and widespread harms.
Boulder would still have to prove causation, he said, including proximate cause — something the companies contend the plaintiffs cannot establish.
The companies focused heavily on that potential breadth in rebuttal.
Shanmugam called Boulder’s theory “astonishing,” arguing that it could eventually extend liability far beyond major fossil fuel producers.
He offered himself as an example.
The theory, Shanmugam said, could allow Boulder to “tag me with personal jurisdiction when I am in Colorado in two weeks and sue me on a nuisance claim for refilling my car and thereby contributing to global climate change.”
He also emphasized the global nature of emissions.
“90 percent of greenhouse gas emissions occur outside the United States,” Shanmugam said, arguing that climate policy “is a matter for the political branches on the federal level in the first instance.”
“Climate change is certainly one of the most pressing issues of the day, but we would submit that this is exactly the wrong way to go about resolving it,” he said in closing.
Kavanaugh also invoked the court’s 2011 decision in American Electric Power Co. v. Connecticut, in which the court held that the Clean Air Act displaced federal common-law claims seeking limits on carbon dioxide emissions from power plants.
He read language from that opinion warning that federal judges lack the technical resources and institutional expertise of specialized agencies when addressing complex greenhouse gas policy.
Kavanaugh asked whether the same concern would apply to a “six-person state jury in Boulder and other juries throughout the country.”
“Those are all good policy arguments about why state law should not apply here,” Russell replied. “But that’s not the question presented here.”
The case has attracted unusually broad participation from states on both sides.
Alabama and 25 other states filed a brief supporting Exxon and Suncor, according to the court docket.
Nineteen state attorneys general filed an August brief supporting Boulder, including Massachusetts Attorney General Andrea Campbell and California Attorney General Rob Bonta.
Those attorneys general argued that traditional state-law claims for fraud, nuisance and consumer deception are not displaced simply because the alleged damages involve climate change.
Their amicus brief supporting Boulder contends states have historically possessed authority to provide remedies for injuries within their borders.
The oil companies and their supporters say allowing those claims would effectively let individual jurisdictions dictate national energy policy through damage awards.
The dispute is significant because nearly 60 governments have brought comparable lawsuits, meaning the Supreme Court’s ruling could determine whether those cases continue toward discovery and trial or are blocked under federal law.
Alito is not participating.
He recused himself Sept. 28, leaving eight justices to decide the case. His absence creates the possibility of a 4-4 split, which would leave the Colorado ruling in place without establishing a national Supreme Court precedent.
The justices did not announce when they will rule.
A decision is expected by the end of the court’s current term in June 2027.
Monday’s arguments made clear that the dispute turns on how the court characterizes Boulder’s lawsuit.
If the justices view it primarily as an effort to impose liability for interstate and global emissions, decades of federal pollution precedent could weigh heavily in favor of Exxon and Suncor.
If they instead view the claims as traditional state-law actions over alleged deception and resulting local injuries, Boulder’s case could be allowed to proceed.
The questions from the bench offered substantial support for both lines of argument but did not reveal a clear majority.
The court must now decide whether Boulder’s lawsuit is fundamentally a state consumer-protection and tort case — or an attempt to use state courts to accomplish what the oil companies say only federal law can do.
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