Ethics question about a rooster.?

Ethics and law are not always the same thing. I'm sure that if anyone has a problem with the rooster, they will talk to the guy about it. You should probably at least let the guy know just to ensure that he realizes what he's doing is illegal. Then he can make the decision about whether or not to keep the bird. You could also let him know that you don't have a problem with it and that you have told no one and don't intend to. Let him know how you feel about the rooster and tell him you hope he gets to keep it.