Wisconsin v. Environmental Protection Agency

The D.C. Circuit granted in part and denied in part a petition challenging EPA's update to the Cross-State Air Pollution Rule. Environmental groups and Delaware argued that EPA violated the CAA by failing to require upwind states to eliminate their significant contributions in accordance with the deadline by which downwind states must comply with the ozone NAAQS. The court agreed, concluding the Agency exceeded its statutory authority under the CAA's "good neighbor" provision by issuing a rule that did not align the upwind states' and downwind states' respective deadlines. The petitioners also argued that EPA made impermissible modeling and implementation choices, and Delaware argued that it should have been designated as a nonattaining downwind state. The court disagreed, finding that the Agency's modeling and implementation choices and its decision to classify Delaware as an attaining downwind state were lawful and rational. It therefore granted the petition in part.