WASHINGTON — The Supreme Court opened its 2026-2027 term on Monday by hearing oral arguments in a high-stakes climate change lawsuit, setting the stage for a decision that could dictate the future of dozens of similar legal battles nationwide.
The case, brought by the city of Boulder, Colorado, targets major fossil fuel companies—specifically Exxon Mobil and the Canadian energy firm Suncor—over the mounting financial costs associated with a warming planet. Across the United States, local governments have increasingly turned to the courts, suing fossil fuel companies for their historical role in driving climate change and seeking compensation to help communities adapt to and repair climate-driven damages.
During two hours of intense questioning, the justices offered no clear indication of how they ultimately intend to rule. However, they did demonstrate a striking level of unison on one fundamental point: identifying who bears legal liability for the sprawling, cumulative impacts of global climate change is an extraordinarily difficult and consequential task.
The legal journey of the Boulder lawsuit has already been winding. Although the litigation was originally filed within the Colorado state court system, the oil and gas companies quickly petitioned the Supreme Court to intervene. The corporations argue that complex, far-reaching climate change matters should not be arbitrated at the state level, contending instead that addressing global climate policy is the exclusive constitutional domain of Congress and the White House. Boulder, conversely, is asking the nation’s highest court to reject the companies’ petition and send the case back to Colorado so that proceedings can continue locally.
With Justice Samuel Alito recusing himself from the proceedings, the remaining eight justices attempted repeatedly throughout the session to distill the immense complexities of the case into something legible and simple. On multiple occasions, justices from both sides of the ideological spectrum posed a direct question to the attorneys: "Why make this argument so complex?" Yet, despite their shared desire for simplicity, the bench rarely agreed on what that simpler underlying legal argument actually ought to be.
Throughout the arguments, the potential consequences for the oil companies weighed heavily on certain segments of the discussion. By contrast, the daily realities and economic consequences faced by communities dealing directly with a warming planet went largely unexplored by the court.
Several judges leaned toward framing the litigation primarily as a back-the-door attempt at reducing greenhouse gas emissions—an interpretation that aligns closely with the defense presented by Exxon Mobil and Suncor. The companies argue that if Boulder’s lawsuit is permitted to move forward, it effectively opens the door for any state court in the country to police industrial activity occurring nationwide, and even across the globe. Under this legal theory, the defendants maintain that no single state law can appropriately be applied to address the cumulative impact of global atmospheric pollution.
"This case involves an unprecedented effort to use state law to regulate global conduct," argued Kannon Shanmugam, the attorney representing the oil and gas companies.
Several justices appeared receptive to that perspective. Justice Brett Kavanaugh noted that he could see no meaningful difference between allowing a state court to order oil and gas companies to pay financial damages for climate-related harms and allowing an individual state to effectively regulate greenhouse gas emissions worldwide. During exchanges with Boulder’s attorney, Kevin Russell, Kavanaugh suggested that Russell was downplaying the severe financial effect the case could have on the industry, warning that widespread liability could ultimately "bankrupt" some of the targeted firms.
In his closing arguments, Shanmugam reinforced the notion that the chaotic and cascading legal consequences of the case could easily scale to match the immense global proportions of climate change itself.
"Boulder could tag me… 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," Shanmugam cautioned the court.
Ironically, these sweeping regulatory concerns stood in stark contrast to what Boulder has repeatedly claimed it wants to achieve through its lawsuit. The city is not asking the judiciary to issue injunctions stopping companies from producing oil and natural gas, nor is it attempting to halt consumers from burning those fuels and releasing greenhouse gases into the atmosphere. Instead, Boulder’s core claim is that fossil fuel companies should be held financially accountable for deceiving the public for decades, obscuring the knowledge that their products were driving large-scale, catastrophic harms through climate change.
Drawing a historical parallel, Justice Elena Kagan argued during the session that Boulder’s approach bears a strong resemblance to the sweeping lawsuits brought by state attorneys general against major cigarette manufacturers in the 1990s. In those historic tobacco cases, states sought substantial financial compensation to cover soaring public health care costs linked directly to smoking consumption. Crucially, the tobacco companies were not ordered to cease selling cigarettes entirely, but they were compelled to roll back deceptive marketing campaigns and fund public awareness initiatives detailing the genuine health risks of smoking.
"This is not an effort to reduce emissions," Kevin Russell, attorney for Boulder, emphasized to the justices. "Under our deception theory, they can continue to produce as much fossil fuels as they like and contribute to as much air pollution and greenhouse gas emissions as the market will bear when consumers are properly informed about the consequences of that decision."
Russell reiterated the compensatory nature of the city’s legal claims later in the arguments, noting, "It doesn’t prohibit them from engaging in the conduct. It requires them to internalize a portion of the cost of their activities by paying for some of the damage."
Justice Kavanaugh dismissed Russell’s phrasing as "cavalier," emphasizing that the financial costs being demanded by local governments could prove astronomical for the oil and gas sector. Indeed, several energy firms, including Suncor, have explicitly warned their corporate shareholders in financial filings that the accumulating wave of climate lawsuits could severely damage their long-term bottom lines.
Shanmugam underscored this point during oral arguments, warning that if the case is allowed to proceed in Colorado courts and Boulder ultimately prevails, it will open the proverbial floodgates for unprecedented litigation.
"More [suits] are being filed by the week… so given the extraordinary magnitude of these cases, where, in each of these cases, plaintiffs are seeking billions of dollars of damages, we need an answer to this question sooner rather than later," Shanmugam told the court.
As is standard practice, the justices heard opening arguments and posed their initial lines of questioning at the very start of the term, but they typically take several months before publishing a final, written decision. The debate over federal preemption and state authority was only one of multiple complex threads the court unpacked during the session, with discussions also touching on the constitutional boundaries of states’ regulatory authorities and the original congressional intent behind the Clean Air Act.
Legal experts note that the justices could ultimately rely on a wide range of distinct judicial rationales for their eventual ruling. Each potential rationale would impact other pending climate lawsuits against oil companies differently, as those various cases depend heavily on their own unique legal foundations and statutory arguments.
"States and local governments are trying to recoup costs related to harms from climate change in a lot of different types of lawsuits," said Erika Kranz, an attorney with Harvard Law School’s environmental and energy law program. Whether these other legal challenges "run into trouble will depend on how justices write their decision."
It remains entirely possible that the justices could ultimately decide to send the case back down to Colorado without issuing a sweeping national ruling—either by concluding that the Supreme Court is not the proper venue to resolve the dispute at this preliminary stage, or by deadlocking in a 4-4 tie. A split decision would leave Boulder free to continue pursuing its lawsuit within the state-level court system. Justice Alito has not publicly explained the precise reason for his recusal, though his participation had previously faced public scrutiny and criticism regarding personal investments in oil and gas companies unrelated to the immediate litigation.
Observers from both sides of the environmental law spectrum point out that while it is difficult to predict the ultimate outcome from oral arguments alone, the intense focus by several justices on the financial exposure of the energy industry suggests profound institutional anxiety over the economic ramifications of climate liability.
Boulder’s legal team now faces the formidable task of convincing the bench that the financial risk to oil and gas corporations is legally irrelevant to the core tort claims being advanced. To succeed, Boulder must successfully overcome skepticism from justices who appeared inclined to view the municipality’s public nuisance claims as a disguised mechanism for regulating national and international emissions through the state judiciary.
"There’s a lot of concern from the oil industry, from corporate actors, and from the conservative justices about the significant consequences of these cases," said Chris Winter, executive director of the Getches-Wilkinson Center at the University of Colorado Law School. "One way to get at that is to equate this case with previous cases, which were much more directly about regulation of pollution."