I need some legal advice regarding a bouncer at a bar....?

The bouncer was charged with ault and battery on a girl who was beaten up so bad the town forced her to press charges and there is now a restraining order against him. He also happens to be the bouncer at a popular bar where he will not let in the little sister of the girl he beat up. I've spoken to the management at the bar who claims that he can't do anything regarding the little sister because she has been cut off from being served before. Is there any type of legal reasoning allowing him to deny her entrance to the bar other than his own personal vendetta without anything in writing that she's caused problems before? Any legal advice would be greatly appreciated.