The Iranian government believes it's being unfairly portrayed in Arma 3.
The near-future military shooter Arma 3 is based on a war between a fractured NATO and resurgent Iran, following its invasion of Greece. It's fairly standard stuff as far as post-Soviet fictional conflicts go, but to absolutely no one's surprise, it doesn't sit too well with the authorities in Iran.
Iran's National Foundation of Computer Games, in conjunction with Iran's Revolutionary Guard Corps, has declared that Iranian military forces are being improperly portrayed in the game as the bad guys, and have thus refused to grant Arma 3 approval for sale in the country. It also issued a statement reminding "all relevant institutions and organizations" that the game is not to be sold without official permission.
It's not terribly surprising that the Iranian authorities dropped the banhammer on Arma 3, as it did the same thing, for similar reasons, late last year with Battlefield 3. It also sentenced a member of the KumaWar development team to death for espionage (the sentence has since been overturned; Hekmati remains in prison awaiting a new trial) and supported the development of anti-West and anti-Israel videogames.
Arma 3 is slated to come out in early 2013, exclusively for the PC.