PC games are very rarely region locked, but on this occasion it appears as though box copies of the game bought in the UK can only be activated in the UK.
OzGameShop sent out an email to members stating the following...
This is an update for our valued customers who have bought one of these titles:
Deus Ex Human Revolution Game PC Deus Ex Human Revolution Limited Edition Game PC Deus Ex Human Revolution Augmented Edition Game PC
These games use Steam to connect to servers which both register the product and allows on-line play, we now have information stating that the publishers have issued a lock on the regions so that only the games distributed to that country/region will have access to use them. Unfortunately we can't guarantee that the version of these title we will be stocking will be fully compatible with your region, we are therefore issuing you with a full refund.
We wanted to inform you straight away to firstly explain the situation and be open and honest with you, the refunds will appear back into the account you made the payment from within the next few working days.
According to 'jaycw2309', an Eidos Admin on the game's official forums, a copy of the game bought in the UK can only be Steam activated in the UK. Once activated, the game can be played anywhere.
According to Eidos, the region lock has to do with DVD space limitations.
Just to be clear to everyone the region lock is just for the retail BOX copies.. ie if you physically buy a box in the UK it will have the uk region code etc, if you buy a boxed copy in russia will be locked to russia, everywhere else is covered by a rest of world region (including poland).
Due to disc size limitations, the languages had to be split onto different masters (PCs dont have universal bluray drives yet so we couldnt put all on 1 disc this is why there is so much confusion)
Also all versions have ALL languages available. So even if you buy the English UK version, you can change the language to French, German etc whenever you want.. The size of the game meant we couldnt fit all languages onto the disc so you will just download the language pack for the game that is all..
It's probably worth noting that digital copies of the game are not region coded.
We've contacted Namco Bandai locally, and will update the story if they provide comment.