Although your question has been accurately answered, since you asked it, I assume it's an issue of concern, so, here's how I dealt with the weapons prohibition during a recent trip to Death Valley...
Got a small Gun Vault and attached it to my truck seat frame with the optional factory security cable. Into the Gun Vault went a Glock, broken down into separate components: frame, slide assembly with barrel in place, 10 round (California legal) magazines. Thus, the gun was disassembled, unloaded, legal, and capable of being restored to functionality in the few moments necessary to manipulate the Gun Vault keypad, fit slide to frame, insert mag, rack slide. Not fast enough for some circumstances, to be sure, but way better than having no gun at hand.
I have visited numerous sites under the jurisdiction of NPS with the weapons ban in place, and have yet to be challenged, searched, or etc. A few years ago, in what has been named to be one of the most dangerous NPS sites, Organ Pipe Cactus National Monument, on the Mexican border, I waved down a ranger to report another party in distress. I was, to any reasonably trained eye, "packing", as was my companion, but this was ignored or at least unmentioned. The ranger was wearing a semiauto handgun with numerous hi-cap mags, and had an 870 and an M16/AR something or other in a Big Sky rack in his truck --- certainly one of the most heavily armed park rangers I've ever encountered. About two weeks later, he or one of his coworkers was killed in a gunfight with Mexican smugglers.
Just because the NPS tries to turn nature into Disneyland, don't forfeit your self-defense options...