Mayor & City Council of Baltimore v. BP p.l.c.

The Maryland Supreme Court affirmed trial court decisions dismissing state common law claims brought by the Mayor and City Council of Baltimore, the City of Annapolis, and Anne Arundel County (the “local governments”) seeking to hold fossil fuel companies liable for harms resulting from climate change. The court’s majority concluded that state common law did not apply to the conduct alleged by the local governments and that, even if state law did apply, the local governments failed to state claims for public and private nuisance, trespass, and strict liability and negligent failure to warn. The court ruled that the Maryland local governments’ state law tort claims involved regulation of interstate and international pollution and would therefore be permitted only under federal law. The court rejected the local governments’ characterization of their claims as seeking redress for “deceptive and misleading commercial conduct” such as alleged concealment and denial of the connection between fossil fuel products and climate change. The court stated that “[n]o amount of creative pleading can masquerade the fact that the local governments are attempting to utilize state law to regulate global conduct that is purportedly causing global harm.” After surveying the “backdrop” of six federal cases concerning application of federal law to claims arising from interstate pollution, the court concluded that the local governments’ claims “fall squarely within the inherently federal areas of interstate pollution and foreign affairs and may therefore only be brought under federal law.” The court therefore held that federal common law displaced any state law claims. The court further concluded that the Clean Air Act would displace any federal common law claims involving national emissions. Citing the Second Circuit’s decision in City of New York v. Chevron Corp., the majority also determined that the Clean Air Act’s enactment did not make state law applicable, “given the federalism concerns undergirding the entire rational of federal common law,” and that the Clean Air Act itself did not authorize states to regulate the conduct at issue in the local governments’ cases. To the extent the local governments’ claims concerned foreign emissions of greenhouse gas emissions, the majority concluded that foreign policy concerns would foreclose any federal common law claims. The court also found that even if the local governments’ claims were not displaced or preempted, they failed to state claims as a matter of law. Regarding the local governments’ public nuisance claim, the court declined to expand common law nuisance to seek damages for conduct governed by an extensive federal statutory and regulatory framework or to require abatement of extraterritorial conduct. Regarding private nuisance, the court wrote that “[a]ssuming without deciding that there is a general public right to be free from adverse effects of climate change, the local governments, as owners of public land, fail to establish that they have suffered an injury that is different in kind from that suffered by members of the public.” Regarding trespass, the court found that the connection between the companies’ alleged activities and the alleged climate change-induced harms to the local governments’ properties was “far too attenuated” to establish a trespass claim. Regarding the failure to warn claims, the court found that the local governments failed to state claims because there was no “duty to warn the entire human race of the effects of climate change” under Maryland’s common law. The chief justice concurred with the majority’s determination that the local governments’ state law claims were preempted but would not have addressed the alternative argument that the local governments failed to state cognizable claims. Another justice wrote a concurring opinion to explain his view that the local governments’ theory of liability was incompatible with tort law. Two justices dissented from the majority’s determination that the local governments’ claims were displaced or preempted. The dissenting opinion stated that it was “clear from the Majority Opinion that it did not decide the case Plaintiffs brought. Rather, it decided the case Defendants described” (i.e., as “suits about emissions, global climate regulation, and the imposition of Maryland tort law on the energy decisions of billions of people worldwide”). In the dissent’s view, the majority’s preemption inquiry had improperly focused on whether the cases’ subject matter “touches” greenhouse gas emissions rather than on the legal duty not to deceive that the local governments claimed the companies violated. The dissent further concluded that even accepting the defendants’ characterization of the local governments’ claims, the majority’s conclusion that the state law claims were preempted was faulty. One of the dissenting justices also would have denied the motions to dismiss the public nuisance and negligent failure to warn claims for failure to state a claim.

The Maryland Supreme Court denied fossil fuel companies’ motion to stay its consideration of the appeals in light of the U.S. Supreme Court granting certiorari to review the Colorado Supreme Court's decision allowing the City of Boulder and Boulder County to proceed with state-law claims to hold fossil fuel defendants liable for the harmful impacts of climate change.

On June 3, 2025, the Mayor & City Council of Baltimore, the City of Annapolis, and Anne Arundel County (the municipalities) filed their opening brief in the Maryland Supreme Court in their appeals of trial court decisions dismissing their climate change cases against fossil fuel industry defendants. The municipalities initially appealed to the Appellate Court; the defendants then filed a petition for writ of certiorari in the Maryland Supreme Court; and the Supreme Court issued a writ of certiorari on April 24, 2025, limited to seven questions, the first of which asked whether the U.S. Constitution and federal law preempted “state law claims seeking redress for injuries allegedly caused by the effects of out-of-state and international greenhouse gas emissions on global climate.” The other six questions related to whether Maryland law precluded nuisance, failure-to-warn, and trespass claims in the context of products produced, promoted, sold, and used around the world and whether the municipalities stated claims for public and private nuisance, strict liability and negligent failure to warn, and trespass. The municipalities argued that their claims were not preempted by federal common law or the Clean Air Act, or barred by any constitutional provision. They disputed the trial courts’ characterization of their claims as operating as “de facto regulation” of greenhouse gas emissions. They also contended that their claims were actionable under Maryland law.