"but couldn't figure out how to find out if someone had a concealed weapon"

Geez. Child's play. You just station a coupla chimps or gorillas at the entrance. They can smell whether someone is packin' a gun, because we can smell the powder burn in the barrel, the gun oil, etc. If they smell a gun on someone, then they grab the bozo, shake him down good, and confiscate the gun. He gets it back when he leaves the libary.

As for yer no smokin' rule, I think that's way outta line.