In my state, there has to be a particular sign (clear sticker on a window or door with white, “no guns” symbol and black and red text) explicitly stating guns aren’t allowed on premises for carry permit holders.
I usually walk away at that point. I’m in IL. You can look up the sign.
Yes, I forgot. There should be a 30.06 sign to ban conceal carry and a 30.07 to ban open carry but I believe the rule is if a store wants to ban all weapons they can post a sign saying that and the police and courts will stand behind that.