I'm doing this from memory, so don't flame me if I got it wrong... Now that carry in National Parks is legal, the common understanding is that carry in the buildings normally used by Park Service personnel is still prohibited because of a pre-existing federal policy or law. The wording was once quoted as prohibiting carry in federal buildings "...except for hunting or other lawful purposes." Or something like that. If the quote is accurate (I'm sure someone can find the federal reg), lawful self defense has always been a lawful purpose. Perhaps there is previous case law to the contrary, but Congress has now passed a law specifically intended to make self defense in National Parks a lawful purpose. Time for our legal eagles to chime in here... BTW, I don't intend to be a test case and don't recommend it to anyone else. Far better to get this clarified in advance.