There are some game developers looking at sanctioned RMT right now because it would be a huge selling point. "Make money playing video games" used to be a popular slogan on tacky banner ads. That could see a comeback in a different way.
Sanctioned RMT works through some official marketplace (think Diablo 3's ill-fated Auction House). Not only does the developer not pay out anything (all money flowing through the auction house is coming from buyers of items), but they even take a "transaction fee" cut. All while continuing to own all the items being traded. There's no downside for the "house".
Except perhaps suddenly running afoul of gambling regulations if they can no longer argue there's no "prize" element to the gambling?
We're well past the point where virtual entitites are imaginable by the general populace.
Getting a virtual gun, creates an actual advantage in the game your are playing online.
While ultimate ownership of the code may be fraught, but practical day to day ownership and usage is not (unless you are fighting a particularly contrived case).
More problematicly, im not sure how youd stop it from extending to say WoW gold-selling, or even cartridges with 100% saves on them.
People will attribute value to anything for any number of reasons, but I’m not sure you can make regulation on anything beyond “encouraging” such behavior. (And I would assume these companies already actively discourage it; you’re not supposed to be able to get money back out of the system!)