Apologies for reviving an old thread, but I was a little surprised no one made the following point:

The museum is city owned, public property, and there is state preemption in Pennsylvania.

Therefore, even open carry should be legal in the museum buildings. Has anyone challenged their no-gun policy? If everyone just conceals and never publicly asserts their right to carry there, it seems like the museum will continue to get away with thumbing its nose at state law.