When being backed-off it is common to be asked to leave the casino. Assuming you have not been formally identified, what is the threshold at which you can consider yourself officially trespassed? Do they need to explicitly declare in a certain way that you are not allowed to be on the property? Is it sufficient for someone to just yell that "you will be arrested if you come back" as you leave the premises? Do you need to be formally identified/notified?

Part of the casino's goal is to harass or intimidate, which means they may attempt to have you arrested regardless of the legal merits. Clearly someone needs to consider if it's even worth risking that experience. In the case someone is willing to deal with the harassment, yet wants to avoid a real conviction for trespassing, what things can/will be used to prove you are in violation of a trespassing ordinance?