But it’s actually “alien-able” meaning that you cannot give away the rights or have them taken away. When I studied property law, and not often since, we learned about restraints on alienation, meaning restrictions on how one could convey land that one owned (as in not allowing property to be sold to minorities, for example).
So the idea is that your rights cannot be taken or lost, even if you do something stupid earlier.
Oops, “in-alien-able”