Pub. L. 105-391, tit. VI, sec. 602
NATIONAL PARK PASSPORT PROGRAM.
SEC. 602. NATIONAL PARK PASSPORT PROGRAM. (a) Program.— The Secretary shall establish a national park passport program. A national park passport shall include a collectible stamp providing the holder admission to all units of the National Park System. (b) Effective Period.— A national park passport stamp shall be effective for a period of 12 months from the date of purchase. (c) Transferability.— A national park passport and stamp shall not be transferable.