The written fee agreement
In France, except in emergencies, force majeure or full legal aid, a lawyer signs a written fee agreement with the client (art. 10 of the law of 31 December 1971). It sets the amount or calculation method of fees and foreseeable costs. A fee based solely on the outcome is prohibited; an additional success fee is allowed.
Source : Légifrance, loi n° 71-1130 du 31 décembre 1971, art. 10