Depends on the state. I believe CO is similar to PA where the owner can put up a sign and if you violate the sign, you're not in violation of any law. HOwever, the owner can ask you to leave. If you refuse, then it's criminal trespass, etc. etc. maybe some weapons offenses thrown in for good measure, etc.When I took my ccw class, the officer who tought the class said that as long as some little old lady doesn't see your firearm on your side in walmart, don't worry about the signs. This came from a cop. You might get a stern talking too if they get called. It's called concealed for a reason. If noone sees it, then no issue.