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MICHIGAN v. EPA Syllabus

of the relevant factors.’ ” Motor Vehicle Mfrs. Assn. of United States, Inc. v. State Farm Mut. Automobile Ins. Co., 463 U. S. 29, 43. Even under the deferential standard of Chevron U. S. A. Inc. v. Natural Resources Defense Council, Inc., 467 U. S. 837, which directs courts to accept an agency’s reasonable resolution of an ambiguity in a statute that the agency administers, id., at 842–843, EPA strayed well beyond the bounds of reasonable interpretation in concluding that cost is not a factor relevant to the appropriateness of regulating power plants. Pp. 5–6. (b) “Appropriate and necessary” is a capacious phrase. Read naturally against the backdrop of established administrative law, this phrase plainly encompasses cost. It is not rational, never mind “appropriate,” to impose billions of dollars in economic costs in return for a few dollars in health or environmental benefits. Statutory context supports this reading. Section 7412(n)(1) required the EPA to conduct three studies, including one that reflects concern about cost, see §7412(n)(1)(B); and the Agency agrees that the term “appropriate and necessary” must be interpreted in light of all three studies. Pp. 6–9. (c) EPA’s counterarguments are unpersuasive. That other Clean Air Act provisions expressly mention cost only shows that §7412(n)(1)(A)’s broad reference to appropriateness encompasses multiple relevant factors, one of which is cost. Similarly, the modest principle of Whitman v. American Trucking Assns., Inc., 531 U. S. 457—when the Clean Air Act expressly directs EPA to regulate on the basis of a discrete factor that does not include cost, the Act should not be read as implicitly allowing consideration of cost anyway—has no bearing on this case. Furthermore, the possibility of considering cost at a later stage, when deciding how much to regulate power plants, does not establish its irrelevance at this stage. And although the Clean Air Act makes cost irrelevant to the initial decision to regulate sources other than power plants, the whole point of having a separate provision for power plants was to treat power plants differently. Pp. 9–12. (d) EPA must consider cost—including cost of compliance—before deciding whether regulation is appropriate and necessary. It will be up to the Agency to decide (as always, within the limits of reasonable interpretation) how to account for cost. Pp. 12–15. 748 F. 3d 1222, reversed and remanded. SCALIA, J., delivered the opinion of the Court, in which ROBERTS, C. J., and KENNEDY, THOMAS, and ALITO, JJ., joined. THOMAS, J., filed a concurring opinion. KAGAN, J., filed a dissenting opinion, in which GINSBURG, BREYER, and SOTOMAYOR, JJ., joined.