Alliance for Cal. Bus. v. State Air Res. Bd.

*1053 We consolidated these cases to address a novel question regarding jurisdiction under the unique and complex cooperative federalism scheme of the federal Clean Air Act ( 42 U.S.C. § 7401 et seq. ) (Act). The Act authorizes the United States Environmental Protection Agency (Agency) to promulgate national primary and secondary ambient air quality standards. ( Id ., §§ 7408, 7409.) States, however, have the "primary responsibility for assuring air quality" and must each devise, adopt, and implement a state implementation plan (SIP) specifying how the state will achieve and maintain the national air quality standards. ( Id. , § 7407(a).) The SIP is submitted to the Agency's administrator (Administrator) for approval. ( Id. , § 7410(a)(1), (a)(3)(B).) Once approved by the Administrator and codified in the Code *25 of Federal Regulations, the SIP becomes federal law and may be enforced "by *1054 either the State, the [Agency], or via citizen suits." ( Bayview Hunters v. Metropolitan Transp. (9th Cir. 2004) 366 F.3d 692 , 695 ; California Dump Truck Owners Ass'n. v. Nichols (9th Cir. 2015) 784 F.3d 500 , 503 ( Dump Truck ).)

The cases here seek the same relief and practical…