Article 1346-5 of the French Civil Code
The debtor may invoke subrogation as soon as he is aware of it, but it may not be set up against him unless he has been notified of it or has taken note of it. Subrogation may be set up against third parties as soon as payment has been made. The debtor may set up against the subrogated creditor the defences inherent in the debt, such as nullity, the defence…