40 CFR § 49.1 - Program overview.

(a) The regulations in this part identify those provisions of the Clean Air Act (Act) for which Indian tribes are or may be treated in the same manner as States. In general, these regulations authorize eligible tribes to have the same rights and responsibilities as States under the Clean Air Act and authorize EPA approval of tribal air quality programs meeting the applicable minimum requirements of the Act.

(b) Nothing in this part shall prevent an Indian tribe from establishing additional or more stringent air quality protection requirements not inconsistent with the Act.