Can you come back after being barred?
A gentle barring like I described earlier is a warning, nothing more.
You're best advised to wait a few months before playing at that casino again, and at least 6 months (a year would be better) before playing on that shift. When you do, be anonymous. Short sessions, no comp card (or a different card), and a small change in appearance.
What do they do if you come back?
Usually they just give you another warning. But if you are especially rude or persistent or playing in such a way that they regard you as a major threat, you may get "trespassed". Which means they read you a warning to the effect that you are not welcome on the casino premises and if you return they will have you arrested for trespassing.
CAN they have you arrested if you come back after that?
It's not entirely clear, but I'd rather not find out firsthand.