Nothing in this subchapter shall be construed as affecting in any way rights of owners and operators of cattle and sheep herds, existing on the date immediately prior to , to trail their herds on traditional courses used by them prior to , and to water their stock, notwithstanding the fact that the lands involving such trails and watering are situated within the park: , That the Secretary may promulgate reasonable regulations providing for the use of such driveways.December 18, 19711971-12-18December 18, 19711971-12-18Provided