16 U.S.C. § 110

All laws applicable to and in force within the Mount Rainier National Park as of January 31, 1931 , and all regulations issued pursuant thereto, are made applicable to and extended over the land added to the said park by section 109 of this title : Provided , That no fee or charge shall be made by the United States for the use of any roads in said park built or maintained exclusively by the State of Washington.