40 C.F.R. § 52.788
Emission limitations and other provisions contained in operating permits issued by the State in accordance with the provisions of the federally approved permit program shall be the applicable requirements of the federally approved State Implementation Plan (SIP) for Indiana for the purpose of sections 112(b) and 113 of the Clean Air Act and shall be enforceable by the United States Environmental Protection Agency (USEPA) and any person in the same manner as other requirements of the SIP. USEPA reserves the right to deem an operating permit not federally enforceable. Such a determination will be made according to appropriate procedures, and be based upon the permit, permit approval procedures or permit requirements which do not conform with the operating permit program requirements or the requirements of USEPA's underlying regulations.
40 C.F.R. §52.788