This is still being litigated in Europe, but at the last decision I can find reference to (in France, Sept 2019) it was ruled that what steam does is sell a lic

This is still being litigated in Europe, but at the last decision I can find reference to (in France, Sept 2019) it was ruled that what steam does is sell a licensed copy. Therefore you can resell the copy you get from Steam and they cannot revoke the license either (excepting maybe some other violations of terms of service like cheating or harassing other players). This hinges on the fact that the license is indefinite. So presumably, this would also hold over Amazon and is probably what most consumers assume is the case. The fact that Amazon also chooses to use the word buy probably makes the applicability even stronger. Edit: where I say "You can resell" it should be understood "You ought to be able to resell" since it is still in appeal.