Sierra Club v. Environmental Protection Agency

The D.C. Circuit held that EPA's determination that it completed sufficient standards to meet CAA §112(c)(6)'s 90% requirement for hazardous air pollutants is a legislative rulemaking subject to APA notice-and-comment requirements. EPA's determination, having declared the end not only of its multi-decade effort of listing and delisting sources subject to regulation under §112(c)(6), but also of any further duty to issue §112(c)(6) standards, clearly purports to bar further demands for additional source-listing or standard-setting. The court, therefore, vacateed the determination and remanded it to EPA to fulfill the notice-and-comment requirements of APA §553.