The U.S. Supreme Court reversed the precedent-setting decision in Connecticut v. American Electric Power Company, Inc.. The Connecticut decision had given standing to several U.S. states, the city of New York and private land trusts to sue AEP for nuissance arising from the production of greenhouse gases. The Supreme Court found that any common law rights of the plaintiffs had been displaced by the authority of the Environmental Protection Agency to regulate greenhouse gases.

AEP and the other defendants are all large utilities who collectively emit 650 million tons of GHGs each year. The plaintiffs alleged that these emissions contributed to climate change which is an ongoing public nuissance that must be abated. The plaintiffs did not seek monetary relief. Instead they sought an order requiring the defendants to cap and reduce their GHG emissions.

New York's Southern District court initially dimissed the lawsuit on the basis that it raised a "political question" that could not be adjudicated by the courts.

That decision was reversed by the Second Circuit Court of Appeals, which found that the political question doctrine does not bar the suit, that all plaintiffs had standing, and that the plaintiffs had made out a successful claim of public nuissance.

The U.S. Supreme Court disagreed. The court split 4-4 on the "political question" issue. In light of the split, the court affirmed the Second Circuit's exercise of jurisdiction. It found unanimously that the plaintiffs' common-law right to seek the abatement of GHGs as contributing to a public nuissance had been displaced by the authority of the Environmental Protection Agency to regulate greenhouse gases. As previously reported, the Supreme Court held in 2007 that the EPA had jurisdiction to regulate GHGs and that the EPA's decision not to do so was "arbitrary, capricious, or otherwise not in accordance with law." The EPA subsequently issued an "endangerment finding" in which it held that "current and projected concentrations of the six key well-mixed greenhouse gases - carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6) - in the atmosphere threaten the public health and welfare of current and future generations."

The court expressly rejected the Second Circuit Court of Appeals' holding that common law rights are only displaced once regulations are in place. Currently, the EPA's regulations under the Clean Air Act are only under development. The EPA currently has several GHG regulatory initiatives underway, including proposed settlement agreements relating to the regulation of power plants and refineries.