Mo. Rev. Stat. § 337.503: Discrimination in promulgation of regulations prohibited.

No official, employee, board, commission, county, municipality, school district, agency of the state, or any other political subdivision thereof shall discriminate between persons licensed under sections 337.500 to 337.540 when promulgating regulations or when requiring or recommending services that legally may be performed by persons licensed under sections 337.500 to 337.540.