Hi,
Perhaps it is not a question of setting up a new organization, but merely registering Wikimedia in France as a foreign corporation so that someone in France or some other EU jurisdiction can act for Wikimedia (i.e. basically be the local agent for Wikimedia)? This would be a Wikimedia "branch". Isn't "branch" an accurate translation of "filiale"?
In French law, there is not such think as a non profit "foreign organisation".
Perhaps someone can review the French law and find out what is necessary to make such a registration in France.
Just set up a French non profit organisation according to the law of July 1901, called in French "association loi de 1901", and add in the status the required articles. The law of July 1901 is very broad. You can make any kind of non profit organisation within this law (sport, cultural, social, humanitarian, etc., at any level: local, national and international). There is no other law regarding non profit organisation.
For example, the "Fondation de France", the biggest foundation in France is set up under this law. Same for "Médecins sans Frontières" (French Doctors).
NB Wikimedia Foundation Inc. is not an "association" but a company or corporation under the definitions commonly used in most jurisdictions.
Alex756
Yann