Hi,
This piece of french legislation has been in for about two years now, but was not advertised outside of france as the money grabbing beaurauctars realised what a money making idea they had come up with....along with the extra speed cameras and police thay now patrol the motorway from Calais, if they stop you for speeding they then ask where is you're Hi-Viz jacket...and wham a double fine.
In thier defence i actually think this is a good idea as when you have broken down or are fixing a flat you are not instantly visable kneeling down or waiting along the hard shoulder for the recovery team and this gives oncoming traffic a better chance of avoiding you....it's just a bit naughty they didn't advertise if to us brits or anyone else.
The bit about all passengers needing one is a suprise as I am sure when the law came out only the driver was required to have one ,I will check this out.

The other things you require by law are a warning triangle ,spare set of bolbs ,snow chains ( in the winter if driving in the alps) and if using you're own car some headlight beam decflectors or beam benders so ou do not dazzle oncoming traffic
Jon.
Jon.