altogether—unreviewable whether the resource-allocation rationale is a sham, unreviewable whether enforcement is declined out of vindictive or personal motives, and unreviewable whether the agency has simply ignored the request for enforcement. But cf. Logan v. Zimmerman Brush Co., 455 U. S. 422 (1982) (due process and equal protection may prevent agency from ignoring complaint). But surely it is a far cry from asserting that agencies must be given substantial leeway in allocating enforcement resources among valid alternatives to suggesting that agency enforcement decisions are presumptively unreviewable no matter what factor caused the agency to stay its hand.
This "presumption of unreviewability" is also a far cry from prior understandings of the Administrative Procedure Act. As the Court acknowledges, the APA presumptively entitles any person "adversely affected or aggrieved by agency action," 5 U. S. C. § 702—which is defined to include the "failure to act," 5 U. S. C. § 551 (13)—to judicial review of that action. That presumption can be defeated if the substantive statute precludes review, § 701(a)(1), or if the action is committed to agency discretion by law, § 701(a)(2), but as Justice Harlan's opinion in Abbott Laboratories v. Gardner, 387 U. S. 136 (1967), made clear in interpreting the APA's judicial review provisions:
"The legislative material elucidating [the APA] manifests a congressional intention that it cover a broad spectrum of administrative actions, and this Court has echoed that theme by noting that the Administrative Procedure Act's 'generous review provisions' must be given a 'hospitable' interpretation.... [O]nly upon a showing of 'clear and convincing evidence' of a contrary legislative intent should the courts restrict access to judicial review." Id., at 140–141 (citations omitted; footnote omitted).
See generally H. R. Rep. No. 1980, 79th Cong., 2d Sess., 41 (1946) (to preclude APA review, a statute "must upon its face
