He helped found and has led the Sons and Daughters of Jewish Deportees from France ("Association des fils et filles des déportés juifs de France)" or FFDJF. It is one of the groups that has documented cases and located former German and French officials for prosecution such as Klaus Barbie, René Bousquet, Jean Leguay, Maurice Papon and Paul Touvier, who have been implicated in the deaths of hundreds of thousands of French and foreign Jews during the Second World War. The Klarsfelds were among organised groups who filed cases decades after the war, sometimes as late as the 1990s, against such officials for their crimes against humanity.