The rule was EPA’s attempt to carry out a court-ordered fix on an earlier version, the 2005 Clean Air Interstate Rule. The court said that the E.P.A. was authorized to set rules that would require upwind states “to bear responsibility for their fair share of the mess in downwind states.” But the E.P.A. had improperly required states “to reduce their emissions by more than their own significant contribution to a downwind state’s nonattainment,” according to the opinion, written by Judge Brett M. Kavanaugh and joined by Judge Thomas B. Griffith. Judge Judith W. Rogers dissented from the ruling.
Several power companies had challenged the E.P.A. rule, and were supported by more than a dozen states, mostly in the South and Midwest. North Carolina supported the rule, along with several mid-Atlantic and New England states.