Some states, like Illinois, being caught in a posted location (assuming the posted sign meets the state requirements and that it is prominently displayed as required) is the same as being caught in a legislatively prohibited place, such as a school. You would face prosecution and likely lose your concealed carry license.
As far as gun owners sometimes being our own worst enemy, the pistol club that I belong to initially was going to prohibit concealed carry by its members when IL finally legalized concealed carry. Fortunately wiser heads prevailed, arguing that those of us in the gun club, NRA members all, who argue with the anti's about responsible gun ownership, would look sadly hypocritical if we refused to honor legal concealed carry. So now we can carry at the indoor ranges, but must keep our loaded and concealed firearm concealed at all times. If you want to shoot your carry gun, you need to have it unloaded and cased before you enter the club. Luckily the local press never got wind of the proposed ban on concealed carry by our governing board.