N.D. Cent. Code § 23.1-06-06
The department may not adopt ambient air quality rules or standards for sulfur dioxide that affect coal conversion facilities or petroleum refineries that are more strict than federal rules or standards under the federal Clean Air Act [ 42 U.S.C. 7401 et seq.], nor may the department adopt ambient air quality rules or standards for sulfur dioxide that affect these facilities and refineries when there are no corresponding federal rules or standards. Any ambient air quality standards that have been adopted by the department for sulfur dioxide that are more strict than federal rules or standards under the federal Clean Air Act, or for which there are no corresponding federal rules or standards, are void as to coal conversion facilities and petroleum refineries. However, the department may adopt rules for dealing with exposures of less than one hour to sulfur dioxide emissions on a source-by-source basis pursuant to any regulatory program for dealing with short-term exposures to sulfur dioxide that may be established under the federal Clean Air Act. Any intervention levels or standards set forth in the rules may not be more strict than federal levels or standards recommended or adopted under the federal program. In adopting the rules, the department shall follow all other provisions of state law governing the department's adoption of ambient air quality rules when there are no mandatory corresponding federal rules or standards.
N.D.C.C. § 23.1-06-06