Wouldn't be able to.
When you purchase a game, you in a way only purchase the media as a way to get the game installed. The CD key if linked to an activation server is what 'allow's you to play the game, its now quite common that once you activate the game against your Steam or Origin client the game is then locked to this account..
selling the media is just that.. selling the install media, doesn't mean the buyer can play the game, unless the game offers a de activate service when you remove the game from your PC.
Its seems odd to buy a boxed retail or digital download title but not be able to sell it on, but this is the way is now been for many PC titles. Effectively when you purchase a game from a high street for all intents the media is pretty much useless.. Its the code inside the DVD box you really need. A shop could sell you the code and you could use any media to install the game, even a torrent lol its that silly... code is what you buy, the media is worthless.