Whether the Clean Air Act permits remand to the EPA to supplement the administrative record with new information and justifications after a rule is promulgated

QUESTION PRESENTED It is a “basic” principle of administrative law that “{aJn agency must defend its actions based on the reasons it gave when it acted.” Dep’t of Homeland Sec. v. Regents of the Univ. of Cal., 591 U.S. 1, 24 (2020). This well-established rule, first articulated in SEC v. Chenery Corp., 318 U.S. 80, 87 (1948), prevents courts from considering an agency’s belated justifications for its decisions. The Clean Air Act doubly protects against the risk of post-hoc justifications proscribed under Chenery by closing the administrative record to information and explanations added after rule promulgation. It limits the administrative record “exclusively” to specified materials compiled from rule proposal to finalization that support the EPA’s bases for its action. 42 U.S.C. §7607(d)(7)(A). And it forbids courts from considering anything that “has not been placed in the docket as of the date of [the rule’s] promulgation.” 42 U.S.C. §7607(d)(6)(C). The Act thus forces the EPA to defend its actions on the materials included in the administrative record at promulgation. However, before conducting merits review on the administrative record at promulgation, the D.C. Circuit remanded the record back to the EPA, allowing the Agency to supplement the record with new materials in an effort to cure a rulemaking defect identified by this Court on emergency review. See Ohio v. EPA, 144 S. Ct. 2040 (2024). The Question Presented is: whether the Clean Air Act permits remand to the EPA to supplement the administrative record with new information and justifications after a rule is promulgated.