"free to leave" isn't really an excuse for tyranny is it? The legality of the sign is derived from the fact that it's on private property, from which the owner

"free to leave" isn't really an excuse for tyranny is it? The legality of the sign is derived from the fact that it's on private property, from which the owner has a right to expel anyone for any reason. Violating the rules of the sign is simply grounds for expulsion from said property, not criminal consequences. That's the difference between a rule and a law.