In medieval times, the border was the wall that had armed guards on it to keep invaders out and the peasants in, so there's precedent there. Everyone lived their lives inside that wall unless their king allowed them to leave. Not allowing someone to leave without permission was documented all the way back to the Romans, in 27 BC when Augustus did not let senators go to the new Roman state, Egypt.

https://en.m.wikipedia.org/wiki/Freedom_of_movement