Page:Michigan v. EPA.pdf/11

Rh *EPA considered availability of controls relevant to the appropriate-and-necessary finding. It thought that doing so was “consistent with” the mercury study’s reference to availability of controls. Id., at 24989.


 * EPA concluded that regulation of power plants would be appropriate and necessary even if a single pollutant emitted by them posed a hazard to health or the environment. It believed that “Congress’ focus” on a single pollutant in the mercury study “support[ed]” this interpretation. Ibid.

EPA has not explained why §7412(n)(1)(B)’s reference to “environmental effects. . . and. . . costs” provides “direct evidence that Congress was concerned with environmental effects,” but not “direct evidence” that it was concerned with cost. Chevron allows agencies to choose among competing reasonable interpretations of a statute; it does not license interpretive gerrymanders under which an agency keeps parts of statutory context it likes while throwing away parts it does not.

EPA identifies a handful of reasons to interpret §7412(n)(1)(A) to mean that cost is irrelevant to the initial decision to regulate. We find those reasons unpersuasive.

EPA points out that other parts of the Clean Air Act expressly mention cost, while §7412(n)(1)(A) does not. But this observation shows only that §7412(n)(1)(A)’s broad reference to appropriateness encompasses multiple relevant factors (which include but are not limited to cost); other provisions’ specific references to cost encompass just cost. It is unreasonable to infer that, by expressly making cost relevant to other decisions, the Act implicitly makes cost irrelevant to the appropriateness of regulating power plants. (By way of analogy, the Fourth Amendment’s Reasonableness Clause requires searches to be