The U.S. Supreme Court heard oral arguments Monday in a case that could determine whether cities and states can hold energy producers legally responsible for damages linked to climate change. The case, brought by the city and county of Boulder, Colorado, targets companies including Suncor and ExxonMobil under state law, seeking compensation for harms allegedly caused by their greenhouse gas emissions. Boulder’s ability to pursue such claims was affirmed by the Colorado Supreme Court in a 5-2 ruling last year, but the issue has sparked intense debate over the role of federal law and interstate commerce in regulating climate-related liability.

During nearly two hours of arguments, several justices voiced skepticism about allowing state and local courts to entertain lawsuits that could impose sweeping financial burdens on the energy industry. Chief Justice John G. Roberts Jr. highlighted concerns about the potential for a surge of similar cases nationwide, noting that a successful claim in Boulder would likely lead to lawsuits filed by municipalities in every state, all seeking substantial damages. He warned this could effectively create a “de facto national energy policy” through litigation rather than legislation.

Justice Brett M. Kavanaugh and Justice Elena Kagan both suggested the federal Clean Air Act may preempt such claims, emphasizing that the regulation of interstate air pollution is a federal matter explicitly assigned to the Environmental Protection Agency (EPA). Kavanaugh cited precedent from a unanimous 2011 Supreme Court ruling, which found the Clean Air Act delegates authority over greenhouse gas regulation to the EPA, thereby limiting the scope for state-level lawsuits. Justice Amy Coney Barrett also raised concerns about states using their courts to impose regulatory measures that would affect other states, questioning whether Colorado could validly attempt to cap emissions nationwide through state litigation.

Opponents of Boulder’s lawsuit—including Republican-led states and energy companies—argue that allowing these claims to proceed threatens to disrupt the nation’s federalist system by enabling one jurisdiction to regulate emissions beyond its borders. They contend that the adjudication of such lawsuits could impose unpredictable, multi-billion-dollar costs on energy producers and potentially other industries that contribute to climate change, far beyond what can be achieved through democratic policymaking.

The litigation comes amid a growing wave of climate-related suits filed by states and municipalities seeking accountability from fossil fuel producers. With Justice Samuel A. Alito having recused himself due to potential conflicts of interest, the court risks a 4-4 split that would leave unresolved the question of whether these cases can move forward. While justices appeared divided on some aspects, the arguments pointed toward a possible conservative majority inclined to block the expansion of climate liability claims under state law.

If the court declines to issue a definitive ruling at this stage, it could soon face numerous additional cases that aim to use the judicial system to address climate change impacts, highlighting the ongoing tension between federal regulatory authority, state sovereignty, and the role of litigation in environmental policy.