A mosque has won an unusual court battle against a Salafist member of the congregation regarded as disruptive and, in an apparent first for Muslims, used France's 1905 law guaranteeing secularism to argue its case.

A court ruled on Wednesday in favor of the small Oullins mosque outside Lyon. It convicted Faouzi Saidi, 51, and fined him 1,500 euros ($1,640) with 500 euros suspended.

Saidi, contacted by telephone, protested that his only error was to "have a big mouth."

Mathieu Allard, lawyer for the mosque, said the court found Saidi guilty of being disruptive by criticizing the imam, holding parallel prayers and preaching his ultraconservative Salafist brand of Islam to converted Muslims.

The 1905 law provides for legal recourse if the ability to express freedom of conscience is compromised.