According to Gary Oldman's management company, Douglas Management Group , the actor will not be voicing General Grievous in Star Wars: Episode III - Revenge of the Sith as has been previously reported.

In addition to some rather nasty comments about actress Samantha Morton (there appears to be some sort of feud developing between the two actors) the DMG website states: "Gary was offered, and agreed to perform in the film, in fact he was excited and looking forward to the work. The snag that made it impossible however is that this film is being made as a non-SAG (Screen Actor's Guild) film. George Lucas and gang agreed to hire Gary Oldman if he in fact would become a union buster, and perform work illegally overseas. As a resident of America, and also a member of SAG, out of respect and solidarity with the other members, he could not and would not consider violating his union's rules."

General Grievous, as describe by the official Star Wars site, is a military mastermind who rises from within the ranks of the Confederacy of Independent Systems. He is part non-humanoid alien, part custom-designed droid. As the site states, "Grievous hunted Jedi for sport and proudly displayed his victims' lightsabers around his belt as trophies of his conquests. His unorthodox fighting form and mechanical enhancements gave him an edge in close-quarters combat, and his strategic ingenuity and flawless cunning rendered him almost invincible against the Jedi."

There's no word on who might step in to replace Oldman, but Lucas should have no trouble finding a suitable voice actor to fill the role.