It depends if you are an amateur or a commercial pilot (for aerial photos for ex). You don't need registration for the time being but another law is being proposed with drone being over 800g required to register and possibly have substantial technological additions on the drone itself (which for now seems about impossible to add such as buzzer in case of freefall, radar reflector)
For now, the rules are here (there's a video and a flyer):
Drones civils : loisir ? activité professionnelle ? - Ministère de l'Environnement, de l'Energie et de la Mer
http://www.developpement-durable.gouv.fr/IMG/pdf/Notice_drones_2015_VFF_web.pdf
The French airspace is pretty crowded therefore totally free fly zone are quite limited
The main rules are :
1- No flight above people
2- Respect of max altitude limits (less than 50m in many places, 150m max elsewhere)
3- Night and out of sight flights are forbidden
4- Forbidden to fly above town in public spaces
5- No drone around big airports (10km)
6- No drone in sensible areas (eg nuclear plants, military sites, some natural areas, local regulation applies)
7- Private life has to be respected
8- No public diffusion of video with people and no commercial use of videos
9- Check that the pilot is covered by an insurance
10- The governing body is DGAC (General Direction of Civil Aviation). In case of doubt, check with them.
Commercial pilots require many other things.
