German Student Union
He returned to France in 1966 to study sociology at the University of Paris's Faculty in Nanterre under the supervision of the network society's theorist Manuel Castells. He soon joined the larger and classic nationwide anarchist federation Fédération anarchiste, which he left in 1967 in favour of the smaller and local Groupe anarchiste de Nanterre and the "Noir et rouge" magazine. Although residing in Paris, he was frequently able to travel back to Germany, where he was notably influenced by the death of Benno Ohnesorg in 1967, and the assault on Rudi Dutschke in April 1968. In this tense context, he invited Karl Dietrich Wolff, leader of the Socialist German Student Union, for a lecture in Paris, which would prove influential to later May events.