Yesterday the U.S. Supreme Court granted three fossil fuel companies’ petition for a writ of certiorari seeking review of the Colorado Supreme Court’s opinion allowing the County Commissioners of Boulder County and the City of Boulder (together, Boulder) to proceed with their state-law claims that the companies are liable for climate change-related injuries suffered by Boulder. Boulder’s suit, filed in 2018, seeks damages and other relief and asserts causes of action for public nuisance, private nuisance, trespass, and unjust enrichment. Boulder alleges that the companies “knowingly caused and contributed to the alteration of the climate by producing, promoting, refining, marketing and selling fossil fuels at levels that have caused and continue to cause climate change, while concealing and/or misrepresenting the dangers associated with fossil fuels’ intended use.” Boulder alleges that as a result of the companies’ actions, Boulder has incurred and will continue to incur substantial costs to protect the City and County’s property and residents from the impacts of climate change, including more frequent and more serious heat waves, wildfires, droughts, and floods.
The case’s history is complex. For the first five years after Boulder filed its case in April 2018, the parties litigated the issue of whether the fossil fuel companies could remove the case to federal court. In September 2019, the federal district court for the District of Colorado remanded the case to state court. The companies’ appeal of the remand order then traveled to the Tenth Circuit, to the U.S. Supreme Court, back to the Tenth Circuit, and finally back to the Supreme Court, which in April 2023 denied the companies’ petition for writ of certiorari seeking review of the Tenth Circuit’s affirmance of the district court’s order remanding the case to state court. However, because the district court and the Tenth Circuit denied the defendants’ requests to stay the district court’s September 2019 remand order, the case also proceeded in the meantime in state court. In June 2024, the Colorado trial court denied a motion to dismiss Boulder’s common law claims. In May 2025, the Colorado Supreme Court concluded that the claims were not preempted by federal law and that the trial court did not err in declining to dismiss the claims.
In their petition for writ of certiorari, the companies—Suncor Energy (U.S.A.) Inc., Suncor Energy Sales Inc., and Exxon Mobil Corporation—asked the Supreme Court to consider the question of “[w]hether federal law precludes state-law claims seeking relief for injuries allegedly caused by the effects of interstate and international greenhouse-gas emissions on the global climate.” In its order granting certiorari, the Court asked the parties to brief both this question and also the additional issue of whether the Court has statutory and Article III jurisdiction to hear the case.
The remainder of this blog post discusses how the Suncor v. Boulder case will proceed, provides an overview of the jurisdictional issues the parties have been asked to brief, and highlights the potential impact on the case of the U.S. Environmental Protection Agency’s (EPA’s) recent rescission of the endangerment finding for greenhouse gases under the Clean Air Act. The post concludes with thoughts on potential near-term impacts on the more than 30 pending cases in which state, Tribal, and local government plaintiffs pursue climate change-focused claims against energy companies, as well as other cases that involve similar preemption issues.
Timeline for Briefing and Argument
Briefing will occur over the spring and summer, and oral argument is expected to be scheduled for the first week of the Court’s October 2026 term.
When this case was previously before the Supreme Court in April 2023 on the companies’ unsuccessful petition for writ of certiorari regarding whether the Tenth Circuit had erred in affirming the remand of the case to Colorado state court, Justice Alito did not participate in the consideration of the petition. The 2023 order did not provide the reason for his recusal.
In Monday’s order granting certiorari, there was no note indicating that any justice had not participated. If that does not change, all nine justices would be participating in the consideration of this case. There is no indication of why Justice Alito appears to have changed his position on recusal in this case.
Does the Supreme Court Have Jurisdiction to Hear the Case?
The Court has directed the parties to brief the issues of whether it has statutory and Article III jurisdiction to hear the case. Under 28 U.S. § 1257(a), the Court’s statutory jurisdiction to review state court decisions extends to “[f]inal judgments or decrees rendered by the highest court of a State in which a decision could be had.”
Boulder argued in its opposition to the companies’ certiorari petition that the Court does not have statutory jurisdiction because the Colorado Supreme Court’s decision is not a “final judgment” since it does not “terminate the litigation between the parties on the merits of the case.”
The fossil fuel companies very briefly touched on this issue in their petition, asserting that the Colorado Supreme Court’s decision fell into one of the four categories of cases that the Supreme Court identified in Cox Broadcasting Corp. v. Cohn, 420 U.S. 469 (1975), as cases in which a state high court’s decision on a federal issue is treated as a “final judgment” for purposes of 28 U.S.C. § 1257. The fossil fuel companies contended that this case fell within the fourth category of cases described in Cox because the Colorado Supreme Court had “finally decided” the federal question (i.e., preemption); that the Supreme Court’s review of the question would be prevented if the companies prevail on the merits on nonfederal grounds; that reversal of the Colorado Supreme Court’s decision would terminate the litigation; and that declining review “would seriously erode significant federal policies.”
In the amicus brief it filed in support of the companies’ petition, the United States also addressed the statutory jurisdictional issue. Although the U.S.’s brief noted the companies’ argument based on Cox, the U.S. primarily contended that under the Court’s 2020 decision in Atlantic Richfield Co. v. Christian, 590 U.S. 1 (2020), the Colorado Supreme Court’s decision was a “final judgment” because the court was exercising its “original jurisdiction” in a “self-contained proceeding,” as opposed to considering an interlocutory appeal from the denial of a motion to dismiss.
In its opposition, Boulder countered both the Cox and the Atlantic Richfield arguments for statutory jurisdiction. Boulder argued that this case does not meet any of the requirements to qualify for the fourth category of exceptions to the final judgment rule in Cox. Boulder argued (1) that the companies raised “a host of other federal defenses on which they could yet prevail,” which could lead to piecemeal appellate review; (2) that reversal of the Colorado Supreme Court would not preclude Boulder’s claims based on deception or for harms resulting from in-state conduct; and (3) that requiring the companies to wait until a final judgment to seek Supreme Court review of the preemption question would not erode any federal policy. Boulder alternatively argued that the fourth Cox exception should be overruled. Regarding Atlantic Richfield, Boulder argued that the procedural context in that case, which involved the Montana Supreme Court, was factually distinct from the procedural context in this case.
Boulder’s opposition noted that the statutory jurisdiction issues had also been presented to the Court when fossil fuel industry defendants unsuccessfully filed a petition for writ of certiorari seeking review of the Hawai‘i Supreme Court’s October 2023 decision allowing the City and County of Honolulu to proceed with state-law climate change-based claims. In its amicus brief in the Honolulu case, the U.S. took the position that the defendants did not meet their burden of showing that the case fit the fourth Cox category. Because the Supreme Court denied certiorari, it did not opine on this issue.
In addition, Boulder raised what Boulder characterized as the “complicated question” of whether the Supreme Court has Article III jurisdiction, arguing that there would only be standing if either (1) Boulder would have had standing to originally bring the suit in federal court or (2) the Colorado Supreme Court’s refusal to dismiss the case inflicted an Article III injury on the fossil fuel companies. Regarding whether Boulder would have had standing, Boulder’s opposition brief noted that the Supreme Court was deadlocked in American Electric Power Co., Inc. v. Connecticut, 564 U.S. 410, 420 (2011), on whether federal courts had jurisdiction over a suit for public nuisance arising from climate-change injuries.
In the fossil fuel companies’ reply brief, the companies allocated just 2½ pages to responding to all of Boulder’s the jurisdictional arguments. The companies characterized Boulder’s Article III arguments as “creative but insubstantial,” disputed Boulder’s efforts to distinguish the case from Atlantic Richfield, and argued that Boulder’s arguments against the application of the Cox fourth category lacked merit.
The parties—and potentially amicus parties as well—will flesh out these jurisdictional arguments in the merits briefing.
What About the Rescission of the Endangerment Finding?
The parties also will further develop their arguments on whether federal law preempts state-law claims for relief for injuries allegedly caused by the climate effects of interstate and international greenhouse gas emissions. One new issue that the merits briefs will confront is the impact of EPA’s finalization of the rescission of the 2009 endangerment finding for greenhouse gas emissions from motor vehicles permitting regulation under the Clean Air Act.
In its brief opposing certiorari, Boulder said that when EPA proposed rescinding the endangerment finding in August 2025, the agency “recognized that this could significantly affect the preemption arguments raised in this case.” Boulder also cited a Wall Street Journal editorial that noted warnings by “[s]ome energy companies” that “withdrawing the endangerment finding could make them vulnerable to lawsuits by states and localities alleging that their emissions cause a public nuisance by contributing to climate change.”
EPA addressed the preemption issue in its final rule, stating that the Clean Air Act “continues to preempt state common-law claims and statutes that seek to regulate out-of-state emissions.” This assertion will certainly be contested in the merits briefing, even as litigation over the legality of EPA’s repeal advances through the courts.
Impacts on the Climate Litigation Landscape
Federal preemption is also one of the primary issues in many of the other pending climate cases brought by state, Tribal, and local governments against fossil fuel industry defendants. For example, the Maryland Supreme Court heard oral arguments, including argument on federal preemption issues, in October 2025 on appeals by Baltimore, Annapolis, and Anne Arundel County of the trial courts’ dismissals of their cases. The question of federal preemption is also at the forefront of the United States’ ongoing lawsuit seeking to block the State of Hawaii’s climate suit against fossil fuel industry defendants. The U.S.’s recently dismissed case seeking to block Michigan from filing such a suit also asserted preemption claims. In addition, lawsuits challenging climate Superfund laws in Vermont and New York involve claims of federal preemption. The New York law has been challenged by the United States, by the U.S. Chamber of Commerce and other business groups, and by 22 states along with fossil fuel trade associations and a mining company. The Vermont law has been challenged by the United States and by the U.S. Chamber of Commerce and American Petroleum Institute.
The courts hearing all these cases may be reticent to delve into preemption questions until the Supreme Court issues a decision in the Suncor v. Boulder case, and fossil fuel companies will likely be interested in stalling the cases in which they are defendants. Courts could of their own volition seek to delay cases. In many of the cases against fossil fuel companies, the defendants may request that cases be put on hold and/or that discovery be stayed, an outcome that plaintiffs generally would not want.
The procedural routes for staying cases or discovery will vary from state to state, but courts generally are afforded discretion to control their dockets. Proceedings in these cases could be suspended for a year or more.
Some of the pending cases, however, are focused on issues that are distinct from the preemption question, and courts might not find it necessary to delay them. For example, New York City’s appeal of the dismissal of its greenwashing action against fossil fuel companies is focused on whether the trial court erred in finding that the City failed to state claims under its consumer protection law and whether such claims were timely. Puerto Rican municipalities could proceed with briefing in their appeal of the dismissal of their federal and Puerto Rico law claims, which a federal district court dismissed as time-barred or on personal jurisdiction and service of process grounds. The Puerto Rican municipalities’ opening brief in the First Circuit is currently due April 13. And Michigan’s recently filed antitrust case against fossil fuel industry defendants may raise such distinct issues that a court would not be receptive to delay.
The Sabin Center will continue to track potential delays and other activity in these cases in the Climate Litigation Database.
Photo: “Supreme Court” by Mark Fischer, CC BY-SA 2.0
Great Job Margaret Barry & the Team @ Climate Law Blog for sharing this story.
