True enough. I was detained years ago (1990? Can’t remember exactly) at the border between the Republic of Ireland and Northern Ireland. I was held for about 24 hours. I’m a US citizen. At that time I was living in France.
In retrospect, I guess, it was understandable. I was crossing the border on a motorcycle with expired US documentation. I had nothing but a French tourist visa, which I’d already overstayed by close to a year. My surname is a common one in a county in the Republic which was often a staging area or hideout area for the IRA. My surname is also the same as one of the H-Block hunger strikers (who was in fact a somewhat distant cousin).
Still, it was scary.