Article 42 of the French Code of civil procedure
The court having territorial jurisdiction shall, unless otherwise provided, be that of the place where the defendant resides. If there are several defendants, the plaintiff shall seise, at his choice, the court of the place where one of them resides. If the defendant has no known domicile or residence, the plaintiff may seise the court of the place where he resides or that of his choice if he resides abroad.