"The Journal Officiel de la République Française has published details of the new breathalyser rules, with drivers advised of the legislation from July until 1 November, 2012 following which fines will be handed out if drivers are not in possession of a kit.
All motorists will have to have a breathalyser, this includes motorcyclists, van drivers and travellers from outside France, with The Local website saying a fine of €11 will be charged to anyone not carrying the breathalyser."

This means that the law won't actually be in force until after Nov 1st but it 's advisable to carry 2 kits just in case one gets used as, if you are stopped by the men in blue, you will still be expected to produce an unused kit.
Alistair