Mo. Rev. Stat. § 390.201
Subject to any exceptions which are applicable under section 307.400, the officers and commercial motor vehicle inspectors of the state highway patrol, the enforcement personnel of the division of motor carrier and railroad safety, and other authorized peace officers of this state and any civil subdivision of this state may enforce any of the provisions of Parts 350 through 399 of Title 49, Code of Federal Regulations, as those regulations have been and may periodically be amended, as they apply to motor vehicles and drivers operating in interstate or intrastate commerce within this state; except that the enforcement personnel of the division of motor carrier and railroad safety shall be authorized to enforce those regulations wholly within the terminals of motor carriers and private carriers by motor vehicle.
§ 390.201, RSMo