They're his films he can change them if he wants to it. You and I may not like it but such is life.
But that's not the whole issue. From what he's said, it seems like Lucas would prefer it if the original theatrical versions deteriorated into nothing, and the sooner the better. Regardless of whether someone has the right to make changes, the "Special Edition" of Star Wars
is not the film that people lined up to see again and again in 1977. It's not the film that changed movie making. IMO that film does not deserve to be erased from history.
We've all heard of classic movies that were re-cut, not preserved or suppressed in some way. We've all heard of film historians and preservationists tracking down original prints to a basement somewhere so an original version can be restored. Why consign Star Wars,
in advance, to that kind of fate? It could all be done now, and wouldn't take anything away from the SE version. I can't understand Lucas's position on that, I just don't get it.
BTW, IMO history will be kinder to the original cuts than the SEs, they are better movies.