As I noted below, today in American Electric Power v. Connecticut the Supreme Court held unanimously that the Clean Air Act displaces federal common law public nuisance claims against emitters of greenhouse gas emissions. It was easy for the justices to agree on this point. Indeed, this outcome was clearly compelled by applicable precedent given the Court’s prior holding, in Massachusetts v. EPA, that greenhouse gases are pollutants subject to Clean Air Act regulation.
Justice Ginsburg’s opinion for the Court applies the Court’s displacement precedents in a straightforward fashion. As prior decisions made clear, but the U.S. Court of Appeals for the Second Circuit failed to comprehend, displacement is the result of legislative action. What matters is what Congress did, not the alacrity or stringency of resulting agency action implementing a statutory mandate. And unlike preemption, displacement does not rest on legislative intent. The mere enactment of federal legislation is enough to displace federal common law causes of action.
“[W]hen Congress addresses a question previously governed by a decision rested on federal common law,” the Court has explained, “the need for such an unusual exercise of law-making by federal courts disappears.” Milwaukee II, 451 U. S., at 314 (holding that amendments to the Clean Water Act displaced the nuisance claim recognized in Milwaukee I). Legislative displacement of federal common law does not require the “same sort of evidence of a clear and manifest [congressional] purpose” demanded for preemption of state law. Id., at 317. . . . The test for whether congressional legislation excludes the declaration of fed-eral common law is simply whether the statute “speak[s] directly to [the] question” at issue. Mobil Oil Corp. v. Higginbotham, 436 U. S. 618, 625 (1978) . . .
We hold that the Clean Air Act and the EPA actions it authorizes displace any federal common law right to seek abatement of carbon-dioxide emissions from fossil-fuel fired power plants. Massachusetts made plain that emissions of carbon dioxide qualify as air pollution subject to regulation under the Act. 549 U. S., at 528–529. And we think it equally plain that the Act “speaks directly” to emissions of carbon dioxide from the defendants’ plants.
That the EPA might not regulate as much as plaintiffs would like – and may not regulate enough to mitigate (let alone eliminate) the public nuisance of global warming – is immaterial. In enacting the Clean Air Act, Congress made the scope and stringency of federal greenhouse gas emissions something for the EPA to determine in the first instance, subject to judicial review.
As Milwaukee II made clear, however, the relevant question for purposes of displacement is “whether the field has been occupied, not whether it has been occupied in a particular manner.” Id., at 324. Of necessity, Congress selects different regulatory regimes to address different problems. Congress could hardly preemptively prohibit every discharge of carbon dioxide unless covered by a permit. . . .
The critical point is that Congress delegated to EPA the decision whether and how to regulate carbon-dioxide emissions from power plants; the delegation is what displaces federal common law. Indeed, were EPA to decline to regulate carbon-dioxide emissions altogether at the conclusion of its ongoing §7411 rulemaking, the federal courts would have no warrant to employ the federal common law of nuisance to upset the agency’s expert determination.
While Justice Ginsburg’s opinion expressly left open the question of whether the Clean Air Act preempts public nuisance claims brought under state law, its displacement discussion explained why courts are particularly ill-suited to addressing climate change claims of this sort.
The appropriate amount of regulation in any particular greenhouse gas-producing sector cannot be prescribed in a vacuum: as with other questions of national or international policy, informed assessment of competing interests is required. Along with the environmental benefit potentially achievable, our Nation’s energy needs and the possibility of economic disruption must weigh in the balance. The Clean Air Act entrusts such complex balancing to EPA in the first instance, in combination with state regulators. . . .
It is altogether fitting that Congress designated an expert agency, here, EPA, as best suited to serve as primary regulator of greenhouse gas emissions. The expert agency is surely better equipped to do the job than individual district judges issuing ad hoc, case-by-case injunctions. Federal judges lack the scientific, economic, and technological resources an agency can utilize in coping with issues of this order. See generally Chevron U. S. A. Inc. v. Natural Resources Defense Council, Inc., 467 U. S. 837, 865–866 (1984). Judges may not commission scientific studies or convene groups of experts for advice, or issue rules under notice-and-comment procedures inviting input by any interested person, or seek the counsel of regulators in the States where the defendants are located. Rather, judges are confined by a record comprising the evidence the parties present. Moreover, federal district judges, sitting as sole adjudicators, lack authority to render precedential decisions binding other judges, even members of the same court.
Notwithstanding these disabilities, the plaintiffs pro-pose that individual federal judges determine, in the first instance, what amount of carbon-dioxide emissions is “unreasonable,” App. 103, 145, and then decide what level of reduction is “practical, feasible and economically viable,” App. 58, 119. These determinations would be made for the defendants named in the two lawsuits launched by the plaintiffs. Similar suits could be mounted, counsel for the States and New York City estimated, against “thousands or hundreds or tens” of other defendants fitting the description “large contributors” to carbon-dioxide emissions. Tr. of Oral Arg. 57.
While the Court’s holding only reached plaintiffs’ federal common law claims, this discussion may give federal courts pause before approving the plaintiffs’ state-law-based claims. Grounding judicial management of climate policy in state common law does not make it any easier. If anything it would be more difficult insofar as different state-law rules could produce different outcomes. We’ll have to see whether lower courts see it that way.