Perhaps if you taxi across an active runway without permission (after being told by the FO to stop) that results in a 747 aborting...or perhaps tear an airplane apart while airborne to rearrange radio boxes you will not be given an invitation to return. Are you aware of anyone else who inquired about coming back and in turn denied? I think each case is reviewed on it's own merits. So if the guy wants to come back just ask...worst case they say no. I do tend to believe however, if you poke someone in the eye on the way out forget about it.