Luminant Generation Company LLC v. Environmental Protection Agency

Issue: (1) Whether, contrary to 42 U.S.C. § 7410"s express limit on the EPA"s disapproval authority and decisions of other courts of appeals, the EPA may substitute its own policy preferences for a state"s about the appropriate means of controlling air pollution within that state, without identifying any applicable "requirement of th[e] [Clean Air Act]" with which the state"s chosen means would interfere; and (2) whether the panel erred under SEC v. Chenery Corp., by upholding agency action based on, and by purporting to "defer" to, an interpretation of the Clean Air Act that the EPA itself not only never adopted " but in fact expressly rejected.