In areas administered by the National Park Service, an individual can possess a firearm if that individual is not otherwise prohibited by law from possessing the firearm and if the possession of the firearm complies with the laws of the state where the park area is located. 54 U.S.C. 104906.
Possession of Firearms in Federal Facilities
Unless expressly authorized, Federal law prohibits the possession of a firearm or other dangerous weapon in NPS facilities. These buildings include, but are not limited to, government offices, visitor centers, ranger stations, fee collection buildings, and maintenance facilities. 18 U.S.C. 930.