In 1979 he became Secretary General of the Comité d'Etude et de Liaison des Intérêts Bretons (CELIB) at Lanester.
Between 1983 and 2000 he was director of the Cultural Institute of Brittany and had an important role in the conception and publication of the collection Les Bretons au-delà des mers : Explorateurs et grands voyageurs (Quimper, Ed.
He strenuously denied this accusation, but made no apologies for his defence of Breton culture and language in the face of the highly centralised French state.
Several organisations also objected to local councils in Brittany disseminating free of charge, in schools, his and his wife Jacqueline's Dictionnaire des romanciers de Bretagne (Keltia Graphic, 1999), dealing with Breton novelists.
Under his own name and under the pseudonym Joseph Bréhier, Le Nail also published numerous articles in newspapers and journals on Breton historical and cultural issues.