A group of men crossing the border into another country was (usually) automatically considered invaders if its size exceeded a certain number.
Eg Iberian Peninsula (Reconquista and later): Foreign parties >10 armed men could not cross without permission between christians and muslims.
Chinese frontier zones, Scythians, Huns, Mongols, Turks etc all had similar rules. If you want to go back further, then Assyria, Egypt, Hittites, Greece had such limits.
You are correct that there are many examples of border control mechanisms, in different levels and ways. Maybe even usually the vast majority for many levels and ways.
Some nations, countries or groups, or other levels, did play with some of those mentioned ideas of less border control mechanisms in some ways or levels, also going back thousands of years.
Countries that were not successful with border control mechanisms, sometimes ceased to exist.
But there are many different levels and ways, and the whole topic is, to put it very mildly, extremely complex.
Eg Iberian Peninsula (Reconquista and later): Foreign parties >10 armed men could not cross without permission between christians and muslims.
Chinese frontier zones, Scythians, Huns, Mongols, Turks etc all had similar rules. If you want to go back further, then Assyria, Egypt, Hittites, Greece had such limits.