Movies
A "work print copy" of Episode III: Revenge of the Sith became available on file-sharing networks early on Thursday.
Tens of thousands of people have already illegally downloaded the film, with one 'tracker' site alone reporting more than 16,000 completions.
Meanwhile, bootleg DVD versions of the release were being sold on the streets of New York City on Thursday for just $5 (£2.75), according to ABC News.
Dan Glickman, President of the MPAA, said in a statement: "My message to illegal file swappers everywhere is plain and simple: You are stealing, it is wrong and you are not anonymous. In short, you can click, but you can't hide."
More: Movies
Movie Reviews
'The Vow' reviewChanning Tatum tries to win back Rachel McAdams in romantic drama The Vow.
At the Movies
This Week's 5 Hottest Movie VideosTrailers for The Avengers and Spider-Man are among this week's highlights in film.
Movies Interviews
Daniel Radcliffe talks 'Woman in Black'The actor talks to Digital Spy about his first post-Potter outing.
Box Office Charts
'Chronicle' leads UK box officeSuperhero drama Chronicle leads the UK box office ahead of Journey 2.
