SumeaLaunchpad (thanks Voodoo Extreme) reports that the rating Half-Life 2 has received from The Pan European Games Information system results in the possibility that there is no rating that will allow the game to be sold in Australia. No decision has been made on the game's fate down under, but here's the cause for concern citied in the article:

The Pan European Games Information (PEGI) age rating system has given Half Life 2 an R(18+) rating. This means that minors are unable to purchase the game in numerous countries like Austria, Belgium, Denmark, Finland, France, Greece, Italy, Norway, Spain, Sweden, and the UK. What's really interesting about this is how the game fares in Australia. The Australian Office of Film & Literature Classification (OFLC) has yet to classify Half Life 2, but if the board follows suit from their European counterparts, it'll mean that one of this years highly anticipated titles is banned outright from sales here. Currently, Australia has no R rating for games, so game titles need to meet the highest rating available (MA 15+) or they will be refused classification.