Mont. Code Ann. § 61-11-215

Nothing contained in this part shall be construed as to repeal, modify, or amend any other laws or parts of laws, or any existing ordinance of any political subdivision relating to the operation or licensing of motor vehicles, the licensing of persons to operate motor vehicles or providing penalties for the violation thereof; nor shall anything in this part be construed so as to preclude the exercise of regulatory powers of any division, agency, department, or political subdivision of this state or of the federal government having the statutory power to regulate the operation and licensing of motor vehicles and the licensing of motor vehicle operators.