yes? And then?
I do not see very well your point paperback, as selling something second hand obviously means that it has been used...
If you buy a house or a flat, do you refrain from buying it because some one else already slept in the bedroom you are going to use?
Except if you meant what I mean in the last paragraph of my post...
The O.P. wishes to transfer a license. a right to play, to someone else, or even do a gift if he wishes.
I am like him: I own Civ 5 on DVD, bought at Amazon.co.uk, and it is something I would like to sell second-hand as I am not pleased with the product...
Amazon always offers the possibility to sell your second-hand item. I asked them: they simply replied that the DVD is "part of the Steam system", and, as such, cannot be transferred without Steam allowing it.
I asked Valve/Steam. They said: it is against their policy. You buy. no refund. No transfer, only if - when buying - you say it will be a gift. With Steam, you can transfer the ownership of a NEW item, not if it has been "used".
The 50$/euro you paid did not give you the right to own the product !
Hence, you may not sell it (you can not sell something you do not own).
Your money bought a 1-way ticket that is barely the RIGHT to use the software.
You and me, we bought it. Even if you did not open the box and never play, the fact that you ACTIVATED the game has consumed your single right to play.
You can only sell the DVD and allow the purchaser to use your Steam account, using your login / password, which, of course, we will never do.
As English is not my language, I hope my explanations make sense...
In other worlds Kooboo, we bought (Steam) toilet paper, and the right to use it.
When used, you cannot sell it back.