At least, it does for now; this may be a Steam issue.
Fans of single player title Metal Gear Rising: Revengeance who bought a Steam version, take note: Steam may be the reason why you can't play the game offline. Steam customers baffled by the game's connectivity issues are venting their spleen on Steam's discussion page. Some who tried to be sneaky and booted up online, then took their machines offline, soon discovered that the game would kick them to the kerb once it realized there was no connection.
The most likely culprit, at least for now, is the Steam API. If that's the case, a fix will probably be on its way within the next few days. In the meantime relax, de-stress and, if absolutely necessary, hide inside a cardboard box until things improve.
Update: Looks as if this one was solved quicker than expected, thanks to Konami.