The Department’s fairly detailed discussion is here. An excerpt:
[Previous] regulations generally prohibited visitors from possessing an operable and loaded firearm in areas administered by [the National Park Service and the Fish and Wildlife Service] unless the firearm is used for lawful hunting activities, target practice in areas designated by special regulations, or other purposes related to the administration of federal lands in Alaska….
[T]he Department’s final rule amends the regulations to allow individuals to carry concealed, loaded, and operable firearms in federal park units and refuges to the extent that they could lawfully do so under non-conflicting state law…. [T]o the extent that a state’s law recognizes licenses issued by other States, including the applicability of reciprocity agreements, the final rule would similarly recognize such reciprocal authorities.
There are FAQ’s here. Some excerpts from that:
Q: Won