Payment of debt not due

When, by mistake of fact or law, as provided in articles 657 onwards, anyone pays what really is not due from him, he may recover what he has paid, on the following terms:- § 1 - Whoever receives the undue payment in bad faith, shall restore it with losses and damages. Where the thing is transmitted to another who is equally in bad faith, the aggrieved party may recover it. But if the recipient was in good faith, only the aggrieved party may recover it if it had been transferred gratuitously and the transferor is found insolvent. § 2 - In respect of the improvements, provisions of articles 499 onwards shall be observed.