That's probably because you were trying to come up with a system this is more restrictive than the traditional physical media system (where you could share or s

That's probably because you were trying to come up with a system this is more restrictive than the traditional physical media system (where you could share or sell a single physical item), but with concessions. There is a very simple and obvious solution - internet connection required on activation or deactivation (for trade). I have not read a single good argument against this system anywhere.