Protecting Americans from Violent Crime Act of 2008 - Bars the promulgation or enforcement of any regulation that prohibits an individual from possessing a firearm, including an assembled or functional firearm, in any unit of the National Park System or the National Wildlife Refuge System if: (1) the individual is not otherwise prohibited by law from possessing the firearm; and (2) the possession of the firearm is in compliance with the law of the state in which the unit is located.