The U.S. Supreme Court opened its new term by hearing oral arguments in the case of Suncor v. Boulder, a dispute that could have sweeping implications for climate litigation in the United States. The central question before the justices is whether local governments, such as the city and county of Boulder, Colorado, can use state law to seek damages from fossil fuel companies for alleged harms caused by climate change, or if such lawsuits are preempted by federal law.
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At issue is the balance of power between state and federal authority over interstate pollution. The outcome of the case could determine whether cities and states have the right to pursue claims against major energy producers, including Suncor Energy and Exxon Mobil, in state courts—or whether such claims must be addressed under federal law. The decision could set a precedent for how courts nationwide handle similar lawsuits brought by municipalities seeking compensation for the impacts of climate change.
Background of the Case
The case stems from a lawsuit filed by Boulder and other Colorado localities against Suncor and Exxon Mobil. The plaintiffs allege that the companies’ fossil fuel activities have contributed to climate change, resulting in damages to local residents and communities. Boulder and its co-plaintiffs argue that they should be able to hold the companies accountable under state law for the costs associated with climate-related harms, such as increased wildfires, droughts, and infrastructure damage.
Suncor’s legal team, led by attorney Kannon Shanmugam, contends that the Constitution and federal statutes—including the Clean Air Act—prohibit states from regulating emissions that cross state lines. Shanmugam argued that allowing state-level lawsuits over interstate pollution would undermine the federal government’s exclusive authority in this area. He told the Court, “the application of state law to certain inherently federal areas” is not permitted, warning that if Boulder’s claims are allowed to proceed, thousands of municipalities could attempt to shape national and international energy policy through jury verdicts and damage awards.
"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. Put simply, that is not the constitutional scheme that the founders adopted."
— Kannon Shanmugam, attorney for Suncor
Supreme Court Justices Weigh In
During oral arguments, the justices pressed both sides on the broader consequences of their positions. Chief Justice John Roberts expressed concern that Boulder’s approach could open the door to a flood of similar lawsuits nationwide, noting that greenhouse gas emissions inevitably affect every state. He questioned whether local lawsuits could become a means for cities and states to influence national energy policy, potentially bypassing federal regulations.
Justice Clarence Thomas asked Boulder’s attorney, Kevin Russell, whether there was any limiting principle to the theory advanced by the plaintiffs. Russell acknowledged that, under their legal theory, large retailers and other entities could also be sued if their actions contributed to widespread harm. “Nothing in our theory prevents that,” Russell said. “When lots of people act together to cause widespread harm, it is not uncommon for multiple different defendants to be liable.”
Justice Brett Kavanaugh referenced Supreme Court precedent, stating that previous decisions have made it clear that interstate air and water pollution are generally matters for federal law, unless Congress has specifically preserved a role for state law. Justice Amy Coney Barrett also questioned whether existing rulings authorize states to apply their own laws to claims involving interstate pollution.
Justice Elena Kagan challenged Suncor’s arguments, suggesting that the company may be conflating the issues of federal preemption and extraterritorial regulation. She pressed Suncor’s attorney to clarify whether the company was arguing that all state law claims related to climate change are preempted by federal law, or only those that attempt to regulate conduct beyond state borders. Justice Ketanji Brown Jackson signaled skepticism about whether the case was ready for Supreme Court review at this stage, raising questions about the procedural posture of the dispute.
Justice Neil Gorsuch raised concerns about the application of state law to conduct with global effects, highlighting the challenge of addressing climate change through local litigation. Roberts also questioned whether Boulder’s lawsuit was an attempt to circumvent previous federal court decisions that have limited state authority over emissions.
Justice Samuel Alito recused himself from participating in the case, as is customary when a justice has a potential conflict of interest. No reason was given for his recusal.
Broader Implications for Climate Litigation
The outcome of Suncor v. Boulder is being closely watched by legal experts, environmental advocates, and the energy industry. The case is part of a broader trend in which municipalities across the country are seeking to hold fossil fuel companies liable for the costs of climate change. If the Supreme Court rules in favor of Boulder, it could pave the way for more state-level lawsuits against energy producers, potentially resulting in significant financial liability for the industry.
Conversely, a decision in favor of Suncor and Exxon Mobil could limit the ability of states and cities to pursue climate-related claims under their own laws, reinforcing the primacy of federal regulation in matters involving interstate pollution and greenhouse gas emissions.
A decision in the case is expected later in the Supreme Court’s term. The ruling could have far-reaching effects on the future of climate litigation and the roles of state and federal governments in addressing the impacts of climate change. Supporters of Boulder’s position did not provide additional comment on the potential national impact of the case.
For more information, the Supreme Court has made the oral argument transcript available to the public.
