29 C.F.R. § 2570.52

This subpart B is effective with respect to all exemptions filed with or initiated by the Department under section 408(a) of ERISA, section 4975(c)(2) of the Code, and/or 5 U.S.C. 8477(c)(3) at any time on or after December 27, 2011. Applications for exemptions under section 408(a) of ERISA, section 4975(c)(2) of the Code, and/or 5 U.S.C. 8477(c)(3) filed on or after September 10, 1990, but before December 27, 2011 are governed by part 2570 of chapter XXV of title 29 of the Code of Federal Regulations (title 29 CFR part 2570 as revised July 1, 1991).