16 U.S.C. § 272c

Nothing in this subchapter shall be construed as affecting in any way any rights of owners and operators of cattle and sheep herds, existing on the date immediately prior to November 12, 1971 , to trail their herds on traditional courses used by them prior to November 12, 1971 , and to water their stock, notwithstanding the fact that the lands involving such trails and watering are situated within the park: Provided , That the Secretary may designate driveways and promulgate reasonable regulations providing for the use of such driveways.