Look up "First Sale Doctrine", especially how it applies to books and copyright law.
Once a lawfully-made copy of a copyrighted work is sold into the free market, the publisher loses the ability to control the future sales of that copy.
Just to add, First Sale Doctrine as written only applies to software distributed on a physical medium, not digitally. When you buy a boxed game you don't gain ownership of the game itself (it's licensed), but you do own the physically media that the game comes on as well as the box and everything included. The law basically says that since you have a right to sell the physical media, the license is thus legally required to follow the disc. People tend to think of the disc as software, but in reality it is only software once it is translated by a computer. Until then you just own a piece of plastic/metal that has pits in it. That is the part you're actually selling....not the software. It's an important distinction.
Software licensed (notice I didn't say sold) through digital distribution is exempt from first sale doctrine for that very reason.
The long and short of it is that the license of a boxed game is tied to the media, whereas a digitally distributed license is tied to the individual who purchased it. Origin/Steamworks etc games get around it by actually just providing a code and a backup copy of the game. The disc is worthless without the account which is tied to the individual, therefore first sale doctrine is once again exempt.
I know alot of this sounds stupid, but if you if you pay attention you'll notice it all makes sense in practice. People keep asking why rights like First Sale Doctrine seem to be blatantly violated, when in fact everything is perfectly legally in the eyes of the law. This is how they will ultimately kill the used market completely.
I'm not saying I agree with it though. I think it's very shady how licensing is done, but it is what it is.
