Article 19 of the French Civil Code

A child born in France of unknown parents is French.

However, he or she will be deemed never to have been French if, during his or her minority, his or her filiation is established with regard to a foreigner and if, in accordance with the national law of his or her author, he or she has the nationality of the latter.

Original in French 🇫🇷

Article 19

Est français l’enfant né en France de parents inconnus.

Toutefois, il sera réputé n’avoir jamais été français si, au cours de sa minorité, sa filiation est établie à l’égard d’un étranger et s’il a, conformément à la loi nationale de son auteur, la nationalité de celui-ci.