i've watched enough People's Court to know that the store owner needs to have signage indicating the conditions, and that the signage must be clearly displayed 
another thing to do, imo, if you really want to fight it, and have the time, is just to stay in the restaurant, and let them call the police
the police can come in and sort it out; if you haven't left the premises, imo, you haven't stolen anything, and the police can decide if a) you're being extorted, or b) you owe the money
another thing to do, imo, if you really want to fight it, and have the time, is just to stay in the restaurant, and let them call the police
the police can come in and sort it out; if you haven't left the premises, imo, you haven't stolen anything, and the police can decide if a) you're being extorted, or b) you owe the money

