40 CFR § 51.1302
Classification and nonattainment area planning provisions
June 9, 2020
An area designated nonattainment for the 2015 ozone NAAQS will be classified in accordance with CAA section 181, as interpreted in §51.1303(a), and will be subject to the requirements of subpart 2 of part D of title I of the CAA that apply for that classification.