The federal position is that the rule for a national  park shall be the same as the rules of the state the park is in.  In Virginia Open Carry is legal.  Furthermore, Virginia has a pre-emption law, the purpose being to  protect lawful citizens from having to be mindful of a myriad of illogical exceptions when exercising their right to bear arms.  Why  should we go against that principal and rule of law in this case. If a law abiding citizen can walk down the street in  Fairfax City while open carrying then by what reasoning would we prohibit the same law abiding citizen from walking in a forest similarly armed?  Lets be self consistent!