40 CFR § 63.50 - Applicability.
(a) General applicability.
(1) The requirements of this section through § 63.56 implement section 112(j) of the Clean Air Act (as amended in 1990). The requirements of this section through § 63.56 apply in each State beginning on the effective date of an approved title V permit program in such State. The requirements of this section through § 63.56 do not apply to research or laboratory activities as defined in § 63.51.
(i) The owner or operator of affected sources within a source category or subcategory under this part that are located at a major source that is subject to an approved title V permit program and for which the Administrator has failed to promulgate emission standards by the section 112(j) deadlines. If title V applicability has been deferred for a source category, then section 112(j) is not applicable for sources in that category within that State, local or tribal jurisdiction until those sources become subject to title V permitting requirements; and
(b) Relationship to State and local requirements. Nothing in §§ 63.50 through 63.56 shall prevent a State or local regulatory agency from imposing more stringent requirements, as a matter of State or local law, than those contained in §§ 63.50 through 63.56.
(c) The procedures in §§ 63.50 through 63.56 apply for each affected source only after the section 112(j) deadline for the source category or subcategory in question has passed, and only until such time as a generally applicable Federal standard governing that source has been promulgated under section 112(d) or 112(h) of the Act. Once a generally applicable Federal standard governing that source has been promulgated, the owner or operator of the affected source and the permitting authority are not required to take any further actions to develop an equivalent emission limitation under section 112(j) of the Act.
(d) Any final equivalent emission limitation for an affected source which is issued by the permitting authority pursuant to §§ 63.50 through 63.56 prior to promulgation of a generally applicable Federal standard governing that source under section 112(d) or 112(h) of the Act shall be deemed an applicable Federal requirement adopted pursuant to section 112(j) of the Act. Each such equivalent emission limitation shall take effect upon issuance of the permit containing that limitation under section 112(j)(5) of the Act, and shall remain applicable to the source until such time as it may be revised or supplanted pursuant to the procedures established by §§ 63.50 through 63.56. Such a final equivalent emission limitation, and all associated requirements adopted pursuant to § 63.52(f)(2), are directly enforceable under Federal law regardless of whether or not any permit in which they may be contained remains in effect.