As some have indicated, the real question is why anybody should feel the need to be armed while attending a town hall meeting or other occasion to hear your elected representative.   I wouldn't take any guns away ( except the assault weapons)--that's just what they want, so they can say "Obama's storm troopers are on the loose".   But I'd take down their ID, including address. And send them home. If they don't want to go home, I'd have somebody monitor them every minute they are close to the meeting.

And I sure as hell would not let them into the meeting.   Just by showing up armed, they have shown how stable they are.   Not likely to contribute constructively.