It seems that Western Europe, in this period at least, has noticeable examples of population and (skilled) workforce moving. Examples can be found of both cities increasing populace (meaning immigration from rural areas into cities) and individual people moving from one city to another, in most cases related to going to university, merchant and banking opportunities, getting a job or invited to court in another city or state (it does not seem to make any difference if the destination is in another country) Often these cases include people exiled from their home city because of politics or debts, but is not limited to that.

I am now interested how would that work legally, bureaucratically, and in practice.
Today to move to another political entity, you need a passport, a visa or work permit (to get which you usually need a lot of your origin country paperwork also). Upon arriving you need to register at the police, tax office, get some kind of local ID, health insurance, etc.

So the questions are:
1) what would you have to do to move back then? Could a free peasant just move into a city, find some work there and stay? Could a skilled craftsmen , without any invitation, move from e.g. Genoa to Lisbon, and start working there?
2) Did they need some sort of permission from local destination authorities?
3) What about permission from their origin country authorities?
4) Upon arrival, did they need some additional paperwork done, like notifying the local council where is their new accomodation?
5) How would they register for taxes?
6) Would they become subjects of the new King or whichever authority was there or would they be still considered subjects to their original one?