Girls: Relationship help?

My friend "Emily" was going out with a guy "Trenton". She broke up with him, but I really think he still likes her. He stares at her all of the time. But the point is my other friend "Hailey" wants to go out with him now. Isn't there some kind of "girl-code" thing though? I personally think he would say no. Anyways do you think it's wrong?