@Relaxed I thought that within the EU they could verify more easily

The Prado database gives description.

Literally it takes a crafty person to fake perfectly an ID. Take a person that know all the details of a certain country document, all its MRZ algorithms, and the job is done. Hence, I could register in any EU country if there wasn't any verification or common database between countries.

People are crafty today, and in my case the employee was not a forensic expert. He simply took the card and sent the scan to the Office des Étrangers. How has the verification been done? Idk

Exactly, but I wouldn't even unconsider it given the strange laws or practices that Italian law is up to. An example could be that they recently started to ask coucil house immigrant applicants estate declaration from their home countries, so this is very outreaching

I mean, I told him that's highly unlikely but he insisted that it was the case.

He told me that authorities eventually informed the Italian Embassy in this country that further informed these other authorities.

Well I don't really know either...but I know that Italy and this country both have peculiar and too outreaching ways of managing things. I mean, this thing wouldn't happen between of said countries and another one like France or US, so for istance there would not be such a thing for an Italian who laterwards took US citizenship or a guy from my origin country taking UK or French citizenship, but as for Italy and this country, my father told me this. I'm not really of what he said but I have to ask, and if that really happened, I would not be surprised, since the nature of these 2 countries.

Because probably I didn't know that one has to declare his own status in an other country, since it regards that other country only? And I asked whether it is LEGAL in the first place

@phoog Thank you for clarifying to Mark Johnson, which every single time he has to moan and complain about my every single question

Let us continue this discussion in chat.

I did not write that they lived in one country only in a city near the border, I did write that I heard that they managed somehow to rent a studio, home or whatever fitted them, gain residency over that in the other country. It could be that they resided with their family in one country (hence not paying rent, or paying little of it) whilst they paid the other one in full, so even the costs are not that big when co-living in one country