"It is not about money, it is an affair of the heart," said Emmanuel Ludot, the lawyer representing the fans.
Walter, president of one of the groups, MJ Community, which has 600 members, attended the first court hearing.
In 2013, Jackson was acquitted of abusing another child, also 13, who had cancer at the time of the alleged offense.
Ludot said the legal battle has the full support of the Jackson family, who have previously called the film a "public lynching."
Ludot says he has been approached by Jackson fan groups from Switzerland, Sweden, Italy and elsewhere, to clear the pop legend's name via the French legal system.