lolwhat?
I'm fairly sure even Steam doesn't allow users to resell their "used" games, despite the DRM.
It's a tricky topic, since there's no real reduction of value for a fully digital product, unlike traditional game releases. On the other hand, why shouldn't people be able to resell a digital game after they've finished it, when they paid the same price for it as, say, a console gamer, or someone who bought a DRM-free physical PC copy.
I suppose one option would be, to only allow the original owner to resell or gift the game once, and to lock down any further account movements of that game.