I don't have an answer to your question but calling that EU is, historically inaccurate at best. "During the 1950s the regime also changed from being openly to

I don't have an answer to your question but calling that EU is, historically inaccurate at best. "During the 1950s the regime also changed from being openly totalitarian and using severe repression to an authoritarian system with limited pluralism. Spain joined the United Nations in 1955 and during the Cold War Franco was one of Europe's foremost anti-communist figures: his regime was assisted by the Western powers, and it was asked to join NATO. Franco died in 1975 at the age of 82." [1] At that point (1975) there was no such thing as the EU (it was called EEC [2] (EEG in my language), and very different from what the EU is today). There where still customs between all members of EEC, except Belgium and The Netherlands. I know this because in the 80s we traveled regularly from The Netherlands to Brussels where my aunt lived as a diplomat for the EEC, while we also bought fuel in Germany which was cheaper than The Netherlands (and there was customs there). The Wikipedia page of EEC [2] is a recommended read if you want to know more about the predecessor of the EU. Apparently, Spain joined in 1986. We went to vacation to Spain multiple times in my youth, including after 1986. We had customs checks. We also had these in France. And we had to take French Francs with us, as well as Spanish Pesetas. I even remember paying with Italian Liras at one point in 90s (1996?) and I felt very rich! [1] https://en.wikipedia.org/wiki/Francoist_Spain https://en.wikipedia.org/wiki/Francoist_Spain [2] https://en.wikipedia.org/wiki/European_Economic_Community https://en.wikipedia.org/wiki/European_Economic_Community