I do that anytime I choose since 2009.
Note: Do not carry in a facility (building) where park employees regularly work. Must have clear and obvious signage restricting.
"The change in federal law basically means that national park visitors must obey the federal, state, and local gun laws appropriate to the parks they are visiting. It's a sharp change to previous laws that severely restricted guns in the national parks, generally requiring them to be locked or stored."
http://abcnews.go.com/Travel/guns-national-parks-firearms-now-allowed-yellowstone-yosemite/story?id=9910171
"In a stinging defeat for gun-control, the U.S. Congress has voted to allow people to carry loaded guns in national parks and wildlife refuges."
http://www.nbcnews.com/id/30832809/...votes-allow-guns-national-parks/#.WqbgjrNG2Uk