Legal to pack a pistol in YNP and all the others too.
Don't try it in Yosemite. The federal law passed in 2009 says that the Park Service cannot ban firearms if state law allows them, but that does not make it legal in all NPs. But, yes, it is legal to carry in Yellowstone and Grand Teton NPs.
I'll second the thought of taking a spotting scope. A few years ago we saw a wolf pack in the Lamar Valley, about nine members feeding on what appeared to be the carcass of a moose calf. They were at least a half mile from the road and we had people lined up to use our scope.
