In a unanimous (8-0) decision, the U.S. Supreme Court ruled in AEP v Conn  that the state and land trust plaintiffs could not invoke a federal common law public nuisance claim against the five largest electric power companies. The plaintiffs in the case were seeking controls on the carbon dioxide emissions from the utilities’ power plants. Building on their 2007 decision in Mass v EPA , the Court held that Congress in passing the Clean Air Act had authorized federal regulation of greenhouse gas emissions and in doing so had effectively “occupied the field” thereby negating any common law claims. In a decision noteworthy for its brevity and clarity, the Court stated:
We hold that the Clean Air Act and EPA actions it authorizes displace any federal common law right to seek abatement of carbon dioxide emissions from fossil-fuel fired plants. Massachusetts made plain that emissions of carbon dioxide qualify as air pollution subject to regulation under the Act. (page 10)
The Court then goes on to describe how EPA is far better positioned than any federal judge to develop emission control requirements to limit greenhouse gas emissions. It reviews the factors contained in the Clean Air Act that EPA must consider, including compliance costs, environmental impact and energy requirements. The Court then states:
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 court judges issuing ad hoc, case-by-case injunctions. (page 14)
The Court also makes clear that any actions or inaction by EPA concerning greenhouse gas regulations would be subject to judicial review. But it states that such challenges are appropriately brought under the Clean Air Act and not as federal common law nuisance claims.
What are the implications of the Supreme Court’s ruling? Will we hear less of the red-hot rhetoric that overzealous, unelected regulators at EPA are stretching the Clean Air Act beyond what was intended in order to regulate greenhouse gases? Will some of the many lawsuits go away that challenge the legitimacy of EPA’s greenhouse gas regulations under the Clean Air Act?
While such changes are unlikely, it should be clear from the Court’s ruling that if EPA’s authority to regulate greenhouse gases were stripped from the Clean Air Act the federal common law nuisance claims could reemerge. The Court narrowly upheld (4-4 vote) the lower court’s ruling granting standing to the plaintiffs, thus leaving the door open for states to bring future actions. It also chose not to rule on whether or not state nuisance law claims were preempted by the existence of the federal Clean Air Act and remanded this issue back to the Second Circuit Court. Justice Sotomayor did not participate in the decision because she was on the Second Circuit when the case was heard by that court.
EPA has already made substantial progress in improving the fuel efficiency of cars and trucks  and has waded cautiously into controls on major stationary sources . The Supreme Court has once again clarified that the structure under the Clean Air Act is in place to address greenhouse gas emissions  and all that is now required is for EPA to continue to do its job.
Steve Seidel is Vice President for Policy Analysis