"We've run afoul of certain prohibitions regarding the depiction of drug use," writes Undead Labs' founder Jeff Strain on the game's forum. "We're working with [publisher] Microsoft to come up with options, including changing names of certain medications in the game to comply with ratings requirements. Whatever our path forward, it's going to take a bit."
Coincidentally, the apocalyptic world of Fallout 3 ran into the same drug-naming issue with the Australians back in 2008. After some editing, the game was suitable for distribution.
"Microsoft is currently evaluating the options with regards to the title's classification," a spokesperson for the publisher told Joystiq. "The Australian Classification system plays an important role in ensuring that Australians can only access age-appropriate games and content."
Strain acknowledged as much in his post, saying, "I know this is frustrating – believe me, we're frustrated too – but each country has the right to set its own rules about content, and it's our responsibility to comply with them. Rest assured we'll do everything we can to find a way to get the game into your hands."
The State of Decay ban comes a day after Saints Row 4 was also refused classification for the region. That game was charged with a similar issue over drugs and Kotaku reports the classification board also raised concern over an "alien anal probe." Publisher Deep Silver is working on edits to make the game suitable for the region.
Despite Australia's R18+ classification for games going into effect earlier this year, it appears real drug names and their effects, along with butt stuff, are still off limits.