The plaintiffs alleged a federal common law nuisance, or state law nuisance in the alternative, and sought injunctive relief in the form of a cap and staged reductions in the defendants' carbon dioxide emissions.

The district court dismissed the complaints as presenting non-justiciable political questions, but the Second Circuit Court of Appeals reversed, holding that the complaints did not present political questions, the plaintiffs had standing, and had stated a claim under federal common law.

The U.S. Supreme Court granted review based on three questions presented:

Whether the plaintiffs had standing;

Whether a cause of action could be implied under federal common law where the Clean Air Act spoke to the same subject matter and assigned regulatory responsibility to the Environmental Protection Agency; and

Whether the claims constituted non-justiciable political questions.

Justice Ginsburg wrote the opinion of the Court and there were no separate dissenting opinions. Only eight justices participated. Justice Sotomayor recused herself, because she had been a member of the Second Circuit panel that decided the case below, although she was elevated to the Supreme Court before the panel issued its opinion.

Justice Alito wrote a brief concurrence, joined by Justice Thomas.

As to standing and the political question doctrine, the Court split equally four votes to four, with the result that the Court of Appeals' decision on these questions was affirmed. Only a single paragraph of Justice Ginsburg's opinion was devoted to these questions.

She explained that four justices adhered to the dissenting opinion in Massachusetts v. EPA, and would hold that none of the plaintiffs had Article III standing, while the other four justices would uphold Article III standing and find no bar to adjudication under the political question doctrine.

Unlikely Ruling

Although this paragraph of the opinion does not have precedential effect, it signals that five justices of the Court are unlikely to rule in the future that federal courts lack jurisdictional authority to adjudicate global warming tort claims.

A major obstacle to climate change tort litigation may thus have been removed.

Previously, all such suits in the federal courts had been rejected—at least at the district court level—based either on the political question doctrine or for lack of standing.

The bulk of the Supreme Court's opinion in American Electric Power was devoted to the Court's determination that any federal common law cause of action had been displaced by the Clean Air Act and the EPA actions it authorizes.  This portion of the opinion includes strong statements about the advantages of decisionmaking by the EPA as an expert administrative agency, in contrast to attempts by federal judges to set emission standards by judicial decree under federal tort law. 

In this respect, the opinion strongly reinforces the Court's conclusion in Massachusetts v. EPA, 549 U.S. 497 (2007), that the EPA has regulatory authority over greenhouse gases as "air pollutants" within the statutory definition (42 U.S.C. § 7602(g)), although the context is now stationary sources rather than motor vehicles.

At the same time, the Court clearly distinguished the displacement of federal common law from the preemption of state common law.   According to the Court, displacement of federal common law results wherever a federal statute "speaks directly to the question at issue," and "does not require the same sort of evidence of a clear and manifest congressional purpose demanded for preemption of state law."   

The opinion includes a single-paragraph discussion of the plaintiffs' state law claims.  The Court declined to address the availability of a claim under state nuisance law because the issue had not been briefed by the parties or addressed by the Second Circuit, and left the matter open for consideration on remand. 

The Supreme Court's decision in American Electric Power will not end climate change tort litigation. The end result of the decision appears to be:

That challenges to the justiciability of such suits in the federal courts (whether articulated in terms of standing or the political question doctrine) are unlikely to succeed before the U.S. Supreme Court, at least barring a significant shift to the right in the composition of the Court

That such suits will be governed by state rather than federal law, apparently meaning the law of the source state where the pollution originated.

Had the Supreme Court determined that federal common law governed tort claims based on greenhouse gas emissions, a single decision by the Supreme Court could have terminated the entire field of litigation.

With state law governing the claims, a simple judicial resolution is far less likely, and litigation on the subject could continue for decades. Another option, of course, is for Congress to intervene by expressly preempting state law.

For the moment, however, that prospect seems unlikely, and any federal legislation addressing climate change would almost certainly require very difficult political compromises.

J. Robert Renner is a partner with Duane Morris in the firm's Los Angeles office. He can be reached at [email protected].