I think that from a purely pragmatic point of view, GL has a right to change the movies that he materially owns. HOWEVER, we are not talking about something that is entirely his work. He's meddling with elements of the story that he didn't write - remembering that he did not direct ESB and ROTJ, nor did he write the scripts or screenplays for any of them. He's not merely changing his own work and vision. It is the work and minds of many people that made the Original Trilogy what it is...erm...was.