Well that seems a bit odd... does this law apply to everyone and all jobs? Cause that sounds far too weird for me to be true. I don't see how it should be a law for people to turn off their phones, while they could actually do that on their own as well.
Well, good for the French I, on the other hand, have a tendency to send work-related emails to my (wonderful, diligent) employees right up to 10pm. And if they aren't acted upon by the following morning, I tend to get pretty damn cranky. So I shan't be moving to France anytime soon.