The Flag of Australia
Australia is a country in the southern hemisphere, a neighbour to New Zealand.
The country's OFLC provides the age classification of all media in the country, including Grand Theft Auto releases. The majority of the GTA series is rated MA15+, however some editions of the games have drawn the RC rating ("Refused Classification"). Grand Theft Auto: San Andreas was famously re-rated after the Hot Coffee debacle, the OFLC changing its original MA15+ rating to RC. The re-release of San Andreas saw it obtain the the MA15+ rating again, after the Hot Coffee material was edited out. Australia has a different version of GTA IV to the rest of the world.
Media that receive a "Refused Classification" rating are banned from sale; it is particularly easy for games to receive this rating, as there is no 18+ classification for games. Games which do receive this rating must be edited to meet MA15+ standards to obtain an Australian release.
Note that the OFLC do not decide ratings policy, but merely enforce it -- changes to the classification system, such as providing an 18+ rating for games, must be authorised with a unanimous vote from all state attorneys-general. Attorney General Michael Atkinson of South Australia is the lone dissenting vote regarding an 18+ category for video games.
Australia within the Grand Theft Auto games
Within the GTA III era games, references are made to a war between the United States and Australia, usually in AmmuNation commercials and radio shows. It can be presumed that Australia lost the war -- San Andreas AmmuNation promotions mention weapons "from when we whooped Australia's ass", and an adoption service commercial in GTA IV mentions "...an Australian baby which loves to play war but always loses."