According to this Reddit post (with screen captures), the DRM checks on several Ubisoft games have been relaxed a little. The post shows screen caps of Assassin’s Creed 2 and Splinter Cell: Conviction being played offline and working fine. The aforementioned titles previously required a constant connection to the internet to run even while playing single-player. This newfound functionality was apparently enabled with some recent patches.
According to the Reddit poster, the games no longer pause instantly if a connection is lost. Of course you will still have to validate the games the first time you play them (and will still require a connection when you first launch them), but - if these screencaps are true - it is a welcomed step in the right direction.