A made-up requirement, in which the centralization of abundance is justified on the basis of scarcity. Even in the feudal period, aristocracy came with obligations, like common access to land for purposes of passage or forage. Basically, this is just an excuse for people to claim more than they are able to use in the present, by asserting the necessity of them being able to do so in the future.

It's how national borders work.

A distinct negative, as far as I am concerned. Passports only became a thing around World War 1. Artificial restrictions on movement by labor is a massive economic distortion that essentially treats labor as a captive resource by mutual agreement between states. Would-be economic migrants whose goal is to work are equated with marauding armies.