You can, but - as they're linked to Steam library, like 'pharrington wrote - whether or not the game will actually launch depends on Steam's opinion on this topic. The game may e.g. refuse to launch until you log in to Steam (and refresh whatever magic DRM sauce it needs on-line).
Could you just make your argument instead of hinting it? Not being a gamer or a full-time developer I have no desire to go off and spend hours figuring out the intricacies of how Steam works to see whether I agree with your assertions or not.
You claim that DRM happens in this particular library. OK, and the practical consequences of that are...?
The practical consequences are that Steam games will call into steam_api.dll to verify whether or not they should run, and will refuse to launch if Steam says so. E.g. if you're logged out of Steam, you'll be asked to log in. Whether or not you can launch a game without an Internet connection active depends on whether or not Steam will allow you to.
This DRM scheme is probably not very solid, though, as I recall replacement versions of steam_api.dll bundled with some bootleg titles.
Do you know the time limits for how long your games can run in Steam's offline mode?