Actually its their game and their contract and they can have it both ways and another four ways too if they want.
Yes. Until one of the contract clauses specifies something that is illegal, in which case that contractual clause is null and void - it doesn't exists, and you can ignore it.
Every content industry, gaming included, hates the first sale doctrine. Actually, every industry hates the first sale doctrine. If the car industry could prevent the sale of used cars, and force you to buy exclusively new cars, they would probably pop the cork, and the cheers would be heard all around the world. But they haven't found a way to go around the first sale doctrine.
(no internet discussion is complete without a car analogy)
A company could try to do so. They'll sell you the car, but only lease you the right to turn on the engine. So you can sell the car, but then, the new buyer would have to get a new engine (or rather the license for an engine). Of course, you wouldn't pay the same amount for this car. And it's clearly a way to get around the first sale doctrine.
The analogy goes even better: if you don't like that car idea, you can go and buy a different car under better terms (it's a different car, since the car manufacturer has a monopoly on its brand).
So why don't the car industry do that? Because if they did, the blatant attempt at weaseling out of the first sale doctrine would be obvious enough, and they'd get crucified. So it's telling that the content industries think they can get away with it, and indeed, they succeed in doing that.