In 1983, Herjean became a founding member of Emgann and served as its secretary for international affairs for several years. He joined Skoazell Vreizh[fr] and served as its secretary-general from 1989 to 2003. In 1984, he organized alongside José Luis Álvarez Santacristina[es] a network for Basque refugees in Brittany.[3]
Herjean died in Guingamp on 6 October 2022, at the age of 78.[4]