42 U.S.C. § 7661e

(a) In general Nothing in this subchapter shall prevent a State, or interstate permitting authority, from establishing additional permitting requirements not inconsistent with this chapter. (b) Permits implementing acid rain provisions The provisions of this subchapter, including provisions regarding schedules for submission and approval or disapproval of permit applications, shall apply to permits implementing the requirements of subchapter IV–A except as modified by that subchapter.