Clifford Chance

In the latest significant decision in the U.S. battles over climate change litigation, the U.S. Supreme Court has once again declined to intervene in a climate tort case filed in U.S. state courts.

On January 13, 2025, the Court denied petitions from several major energy companies seeking to overturn a Hawaii Supreme Court decision that had allowed a state tort case to proceed. As a result, state courts will continue to be the primary battlegrounds for climate change-related tort claims in the United States, setting the stage for a series of further confrontations in courtrooms across the country.

The state court complaint, in City and County of Honolulu et al v. Sunoco LP et al., alleged that energy companies misled the public about climate-change related dangers posed by burning fossil fuels, leading to damages. In response, the companies argued that the plaintiffs' state tort claims were preempted by the federal Clean Air Act. This issue went to the Supreme Court of Hawaii on an interlocutory basis before trial. That court refused to dismiss the lawsuit, holding that the Clean Air Act does not preempt state law claims seeking damages within the state caused by the effects of "transboundary" greenhouse gas emissions, meaning emissions generated from outside the state. The companies then petitioned the U.S. Supreme Court for review.

The U.S. Supreme Court denied the petition without explanation, which is its standard practice. This denial means that the case may now proceed in a trial court in Hawaii. And while this is only an interim development in a single case, litigants across the country have been closely watching this petition to see whether the U.S. Supreme Court would intervene in the wave of state court climate litigation or whether it would let the cases run their course. For now, we expect the litigation to continue, with state courts continuing to be the primary venue for climate change-related tort claims.

This conflict is only the latest skirmish in a long battle between state and local governments seeking to force action on climate change through litigation and defendant companies that argue that the issue is more appropriately addressed through the legislature. The parties' strategies in these suits vary and continue to evolve. Plaintiffs have tended to file the cases in state courts, while defendants have sought to "remove" the cases from state court to federal court to address the federal preemption question and to avoid facing conflicting outcomes under a web of state and local laws. For years these cases were tied up in procedural battles over whether the cases belong in federal or state court, with little action on the substantive claims. The outcomes have generally favored state courts, and in early 2023, the Supreme Court declined to intervene. This latest Supreme Court petition is an output of one of those state court cases, and we can expect to see more as the cases progress.

Adding another layer of complexity, in considering the energy companies' petition the Supreme Court asked for the views of the U.S. Solicitor General, who is Department of Justice's representative tasked with arguing the federal position in Supreme Court cases. The Solicitor General submitted a brief urging the Supreme Court not to accept the case for review, on the basis that the plaintiffs were raising state law claims. With the transition to the new Trump Administration, it is possible that the federal position will change in future climate cases.

Honolulu's lawsuit is one of dozens of climate cases filed by state and local governments in the last decade. And while the Honolulu lawsuit gave the Supreme Court a chance to decisively address the preemption issue that has muddled climate litigation for years, the Court has declined. This decision allows the climate suit brought by the city and county of Honolulu to proceed, opening the door for other cases to progress through the factfinding discovery process, potentially to trial and possibly encouraging the filing of more, similar cases. And because each state court may interpret and apply state tort laws differently, and many have unique procedural rules and evidentiary standards, we can expect to see a wide variety of outcomes depending on the jurisdiction, leading to a complex and fragmented and legal landscape. While these developments may lead the Supreme Court to intervene in the future, for now the Court seems willing to allow these cases to develop. It will be important to monitor how these cases progress in the coming months and years.