I lived for a few years within the boundaries of the European Union. As an American I was entitled to stay for 90 days. But there was a natural loophole that allowed me to remain.
Prior to the elimination of border controls between Schengen states, each country specified how long a visitor could stay. There would then also be a specified period of time required to "reset the clock" time outside of the country before one could visit again.
After the integration of states, a person with access to one could travel between them or stay within any one with no record that they had done so. And since there was no mechanism of communication between countries vis-a-vis federalized immigration control, there was no normal way of checking how long a person had been within the newly-unionizing superstate.
At least that's how it worked for me. That's how it worked, traveling (or not) with an American passport as identification.
... The loophole created by the epochal changing of European international law.
After my passport was stamped in Brussels, no border-control agent looked at my documentation again until I went to Ireland, which (with the UK) is outside of the Schengen area.
I stayed in the Netherlands and in Spain for about extended periods with no scrutiny. In Ireland, I was never called a foreigner.
Nobody on the Continent knew how long I had been in their country, because they'd eliminated border controls and nobody knew how long I'd been within the EU, because that part of the agreement hadn't been worked out yet.