There are no defenses specifically applicable to money laundering offenses. Only common criminal law affirmative defenses (error of law, state of necessity, etc.) are potentially applicable, but such defenses are rarely upheld.
Some defenses can however apply to the persons subject to reporting obligations, who reports the money laundering offense. They cannot be prosecuted (Art. L. 561-22 of the French Financial Monetary Code) for slanderous denunciation (Art. 226-10 of the French Criminal Code) or breach of professional secrecy (Art. 226-13 and 226-14 of the French Criminal Code).