Supreme Court to Address Climate Change Lawsuit in October 2026 Term
The Supreme Court is set to kick off its October 2026 term with a significant case centered on climate change litigation. This pivotal case will tackle the contentious issue of whether federal law can override state lawsuits addressing the impact of climate change.
In the case of Suncor Energy (U.S.A.) Inc. v. County Commissioners of Boulder County, the Supreme Court will explore the reach of the federal government’s authority in preempting environmental lawsuits initiated by local governments in state courts. Central to this investigation is the Supremacy Clause found in Article VI, Clause 2, which asserts the dominance of federal law over state laws.
This legal battle began when Boulder County and the city of Boulder, Colorado, filed a complaint against Suncor Energy, Suncor Energy Sales, and Exxon Mobile in 2018. They argued for a state court’s intervention to make these energy companies contribute financially to the environmental challenges their alleged actions have caused. Critics have likened this financial obligation to an indirect carbon tax.
Initially, a state trial court sided with Boulder, permitting the case to proceed in the state legal system. This decision was upheld by the Colorado Supreme Court, which emphasized that the lawsuit focused on “deceptive conduct and ‘upstream production activities,’” rather than directly regulating greenhouse gas emissions.
Suncor, dissatisfied with the state court’s ruling, escalated the issue to the U.S. Supreme Court. The primary question before the justices is whether federal law can negate state-law claims related to the impact of interstate and international greenhouse-gas emissions on climate change. Additionally, the Court will consider if they possess the jurisdiction necessary to adjudicate this matter.
The Underlying Dispute
Suncor, in its appeal, highlighted the rising tide of lawsuits targeting fossil fuel companies in state courts nationwide for damages purportedly linked to greenhouse-gas emissions and global climate change. It challenged Boulder’s stance, arguing that the federal Clean Air Act should override state tort laws in these instances.
According to Suncor, this case presents one of the most critical unresolved questions about the interplay between state and federal laws. They urged the Supreme Court to determine if the state-law claims, put forth by numerous states and municipalities, are viable before the energy sector faces potentially substantial legal judgments.
Boulder initially chose not to respond to Suncor’s petition, but at the Supreme Court’s request, they submitted a reply in November 2025. In their brief, Boulder pointed out that the Court had previously declined to review similar issues in other cases, such as Sunoco LP v. City & County of Honolulu (2025). They argued that addressing this case could lead the Court into a complex web of preliminary issues.
Furthermore, Boulder contended that the Supreme Court lacks the authority to review an interlocutory decision from the Colorado Supreme Court and that resolving the case would necessitate tackling intricate questions of Article III jurisdiction.
Latest Developments and Arguments
In a brief from Deputy Solicitor General Sarah M. Harris, the United States voiced support for Suncor’s case. Harris argued, “Can one city wield one State’s law to dictate how the rest of the world must address a global problem with global effects? The Constitution supplies the answer: Absolutely not.” She emphasized that the Clean Air Act should preempt Boulder’s claims.
Suncor reiterated its position in a May 2026 brief, contending that using state tort law to address global climate change contradicts constitutional principles and undermines the federal regulatory framework established by the Clean Air Act.
Meanwhile, in a recent brief, Boulder maintained that the Clean Air Act does not preempt their claims and criticized Suncor’s interpretation of the Act. They insisted that jurisdictional issues should be the focal point of the case.
The significance of Suncor v. Boulder is underscored by the filing of over 70 amicus briefs since the Supreme Court agreed to hear the case, with contributions from political leaders, legal experts, and various interest groups.
Original Story at constitutioncenter.org