Leon joined the international sporting commission of the FIA at the start of 1972 to work in the administration of the federation's sporting activities. He became secretary-general in June 1976 and when the CSI was made independent of the FIA at the end of 1978 he was named secretary-general of the FISA, a role which he held throughout the years in which Jean-Marie Balestre was in charge of the federation.At the end of 1991, soon after Balestre was defeated in the election by Max Mosley for the FIA presidency Leon was replaced as secretary-general of the organization by Pierre de Coninck. Leon was given a new role as head of the FISA Manufacturers' Commission, which had been Mosley's former role. He remained in that role when the FISA was abolished and absorbed into the FIA and in 1996 stood in the election to be president of the FFSA, the French motorsport federation. He was defeated in that election by Jacques Regis.In the autumn of 2000 Leon was appointed head of the international karting federation and began a major restructuring of the sport which resulted in the introduction of new rules, regulations and championships.