American Lung Association v. EME Homer City Generation

Holding: The Clean Air Act directs the Environmental Protection Agency (EPA) to establish national ambient air quality standards (NAAQS) for pollutants at levels that will protect public health. Once EPA settles on a NAAQS, the Agency must designate "nonattainment" areas, i.e., locations where the concentration of a regulated pollutant exceeds the NAAQS, and each state must submit a State Implementation Plan, or SIP, to EPA within three years of any new or revised NAAQS. From the date EPA determines that a State SIP is inadequate, EPA has two years to promulgate a Federal Implementation Plan, or FIP. Among other things, the CAA mandates SIP compliance with the Good Neighbor Provision, which requires SIPs to "contain adequate provisions . . . prohibiting . . . any source or other type of emissions activity within the State from emitting any air pollutant in amounts which will . . . contribute significantly to nonattainment in, or interfere with maintenance by, any other State with respect to any" NAAQS. The CAA does not require that states be given a second opportunity to file a SIP after EPA has quantified the state's interstate pollution obligations. Nor does the Good Neighbor Provision require EPA to disregard costs and consider exclusively each upwind state's physically proportionate responsibility for each downwind air quality problem. EPA's cost-effective allocation of emission reductions among upwind states is a permissible, workable, and equitable interpretation of the Good Neighbor Provision.

Judgment: Reversed and remanded, 6-2, in an opinion by Justice Ginsburg on April 29, 2014. Justice Scalia filed a dissenting opinion, in which Justice Thomas joined. (Alito, J., recused)