This happened at the High Museum in Atlanta, Georgia. Guy has a Georgia carry permit. Georgia has a new “guns everywhere” law. Guy first checks website of the museum — nothing on it about weapons being prohibited. Guy and his wife go to museum. He’s open carrying. No “guns prohibited” sign on the door. Guy finds himself surrounded by security guards. From 11 Alive TV:

Ariemma says they took his gun from him, took it apart, escorted him outside, watched him place the pieces inside the trunk of his car, then escorted him back to his wife, inside.

At one point, he says, one of the security officers said something about the museum’s policy on guns. “They said, ‘We’re sorry, we should have had it posted on the door, we should have had it on the website.’ I said, look I’m sorry, but it wasn’t posted or I would have gladly abided by the rules, and I would have put the gun back in the car.

Video at the link. Incidentally, later that same day, suddenly there was a notice on the museum’s website stating that guns are not allowed.