Yeah I THINK it's a civil case/ matter between you and the theater. I ain't been to a movie theater in so long that I never think about it. But I would never willingly be another fish in the barrel which is what that sign makes of most patrons.they just simply ask you to leave
There's guys here that would tell you to give the theater management the middle finger and tell them why. There's also guys that would tell you to ignore the sign and carry on about your business. I kinda identify with the latter group. But if you go that route you will have to go more deep concealment as in a Bodyguard 380, G42/G43 etc.
Those signs are everywhere now. Entire shopping malls forbid it. And given the desperate circumstances of most malls they should welcome any law abiding customers with money.
Anyway the way I see it is it's between you and the property owners. You might get banned from the property or a civil suit filed against you but I don't think you're anywhere near felony range.