For what it’s worth, the 70mm print of Star Wars screened publicly at the Academy last year was said to have been given special authorization by George Lucas, which corroborates Pablo’s inferred statement. You are correct that no one has directly said in absolute terms that George Lucas is the one preventing the release of these films, but it’s been so heavily implied and talked around that there’s no real reason to assume anything different. We can only speculate as to the “why,” but the “who” is pretty clear. It’s George Lucas. It’s always been George Lucas. He doesn’t want them released and the current rights holders are either unable (less likely, in my opinion) or unwilling (more likely) to go against those wishes.