Sierra Club v. Environmental Protection Agency

Acting under the Clean Air Act (CAA), the Environmental Protection Agency (EPA) (defendant) established the National Ambient Air Quality Standards (NAAQS). The NAAQS set the acceptable concentration levels for various air pollutants. States were required to adopt state implementation plans (SIPs) to implement and maintain NAAQS compliance. The CAA prevented federal funding for projects that did not conform to a state’s SIP. At Congress’s direction, the EPA promulgated procedures for assessing NAAQS conformity for proposed transportation projects. In 2010, the EPA issued revised guidance (2010 guidance) for assessing NAAQS compliance. The 2010 guidance, which was issued after notice and an opportunity for public comment, identified a preferred methodology for calculating compliance but noted that the EPA would consider alternative methods on a case-by-case basis. In 2015, the EPA issued new guidance (2015 guidance), changing the preferred methodology. The 2015 guidance, which also noted openness to alternative methods on a case-by-case basis, was issued without a notice-and-comment process. Various environmental and community organizations, including the Sierra Club (collectively, Sierra) (plaintiffs) believed the 2015 guidance would make federal funding more likely for transportation projects at the margins of NAAQS compliance. They sued the EPA, arguing that by modifying the calculation methodology without notice and comment, the EPA violated both the Administrative Procedure Act and the CAA. The court of appeals considered whether it had jurisdiction over Sierra’s petition.