The co-op mode in the modified Australian version of the new Saints Row IV will be incompatible with versions played by the rest of the world.
According to a post on the official Saints Row IV Facebook page the omission of a particular 'loyalty' program which featured depictions of 'alien narcotics' is the cause of the issue.
The post explains, "we had to cut one optional Loyalty Mission from the game. Loyalty Missions are optional side missions that you can do with your homies. This mission in particular involves alien narcotics in the simulation, which eventually have a positive effect in terms of gameplay. As you can not depict any positive effect for using narcotics in video games in Australia, this was the reason the game was refused a classification."
They go on to say "While we are very proud of all our different missions, we do feel that Saints Row IV on the whole remains largely the same without this single optional mission, and we also feel that you deserve to know what you are getting in Australia. Due to the changes we were forced to make, this version is different than the version rated by rating boards like the ESRB, USK, and PEGI, which is why it will be incompatible with those versions in co-op."
Neighboring New Zealand, however, will receive the full, unedited version of the game.
For more information on the Saints Row IV licensing debacle click the link here.