Anjouists love to erroneously claim that Henri IV, because he was born in Bearn, Kingdom of Navarre, was a foreigner or lost his quality as French.
This is flatly wrong. The Parlement de Paris ruled in 1505 that Bearnais were naturally French. The general prosecutor for the Crown even went as far as to proclaim that Bearn was “part of the Kingdom of France,” even if it wasn’t technically true. Regardless, this shows that the Crown wanted Bearn to be under its suzerainty. The judgment was confirmed again in November of 1579, when Bearnais were held as “French and regnicole.”
Further, the Kingdom of Navarre was a tiny de facto vassal state. The Spanish had conquered all of Iberian Navarre, leaving only Bearn and Basse-Navarre as the “Kingdom” of Navarre.
This tiny state was ruled by French vassals and had previously been in personal union with the Kingdom of France. And long before that, Bearn had been part of the “ancient domain” of Francia and West Francia.
This means that Bearn was not considered a foreign country. Thus, under the principle of jus soli (the standard at the time), Henri IV was French at birth and a régnicole.
This means, ever since the creation of the Fundamental laws in the 16th century, no foreigner has ruled France. And ever since the Hundred Years’ War, every foreigner has been rejected in favour of the French claimant.
The French Unionist Project 