The movie is available to purchase, so why is the game based on the film banned? Australia's Office of Film & Literature Classification gave the film version a rating of R18, restricted for those under the age of 18, but video games ratings only go to MA15+, restricted for those under the age of 15. Therefore, the game would be rated R18, but since no rating exists for gaming, the OFLC refuses to classify the game. Not having classification, unless under certain rules of exemption, effectively bans a game from sale throughout the country. Atari, who would distribute the game for Eidos in Australia, will not try to resubmit an edited version of the game.
The OFLC's lack of R18 for video games has been a subject of much contention. As written in 1973 by the Attorney General of Australia (5th paragraph -- pdf file), "adults should be entitled to read, hear and view what they wish in private and public," provided others are not forced to view offensive material. We understand, to a point, censorship to protect the youth, but give grownups the right to game however they please.
[via Game Politics]