I’m also not going to argue the legality of it. You can buy and sell used games. That’s not in question.
It’s true that a software license is simply a license to use and while that license gives you no ownership of the actual intellectual property, it does give you license to use the product. You agree to those terms when you install the product.
There is quite a bit of case law that exists for Copyright and Software. And some of it even says that one of the things Software companies can’t do is enforce a term that limits your ability to transfer the license to another party. It’s viewed in the same way that Books or Music copyright is administered.
BUT – unlike Books or Music, Software often needs to be supported long after the initial purchase or sale. This support comes in the form of patches and game updates. And, in many cases, some online service component that the game provides for multiplayer access.
Now the question I would raise is whether or not the right to continued support is something that should be transferable with that license to use?
I don’t think so.
In my mind, the right to use and the right to support are two separate items. Copyright law supports your right to use. It doesn’t support your right for support.
As I see it, a gaming company should be entirely within their right to provide a key for this support with the original purchase and then deny that key to anyone purchasing the product on the secondary market. There are plenty of examples of non-transferable warranties for non-software products.
To me, that’s entirely fair. If you buy a used game, then you buy an unsupported game.