40 CFR 57.101: Purpose and scope.

(a) Applicability of the regulations. The regulations in subparts A through H govern:

(1) The eligibility of smelters for a Primary Nonferrous Smelter Order (NSO) under section 119 of the Clean Air Act;

(2) The procedures through which an NSO can be approved or issued by EPA; and

(3) The minimum contents of each NSO required for EPA issuance or approval under section 119. Subpart I et seq., will contain NSOs in effect for individual smelters.

(b) State authority to adopt more stringent requirements. Nothing in this part shall preclude a State from imposing more stringent requirements, as provided by section 116 of the Clean Air Act.