36 CFR § 7.13
(1) Notwithstanding the prohibition of commercial vehicles set forth in § 5.6 of this chapter, commercial vehicles are allowed to operate on U.S. Highway 191 in accordance with the provisions of this section.
(2) The transporting on U.S. Highway 191 of any substance or combination of substances, including any hazardous substance, hazardous material, or hazardous waste as defined in 49 CFR 171.8 that requires placarding of the transport vehicle in accordance with 49 CFR 177.823 or any marine pollutant that requires marking as defined in 49 CFR Subtitle B, is prohibited; provided, however, that the superintendent may issue permits and establish terms and conditions for the transportation of hazardous materials on U.S. Highway 191 in emergencies or when such transportation is necessary for access to lands within or adjacent to the park area.
(3) The operator of a motor vehicle transporting any hazardous substance, hazardous material, hazardous waste, or marine pollutant in accordance with a permit issued under this section is not relieved in any manner from complying with all applicable regulations in 49 CFR Subtitle B, or with any other State or federal laws and regulations applicable to the transportation of any hazardous substance, hazardous material, hazardous waste, or marine pollutant.
(4) The superintendent may require a permit and establish terms and conditions for the operation of a commercial vehicle on any park road in accordance with § 1.6 of this chapter. The superintendent may charge a fee for permits in accordance with a fee schedule established annually.
(5) Operating without, or violating a term or condition of, a permit issued in accordance with this section is prohibited. In addition, violating a term or condition of a permit may result in the suspension or revocation of the permit.