Allyson,
From about the middle of last year certain speed camera "detecters" are permitted in France.
The defining method is:
Advertisers, such as GPS systems, Sat Nav etc, that give you the location of fixed cameras ARE legal to use in France.
Detectors, such as Snoopers, Road Angel etc than can detect the laser type etc of the mobile units are NOT legal to use in France.
If you are found in posession of one of the detector types, it does not even have to be in operation!!!! it is illegal to own one in France, the Gendarmes will confiscate it & as Euro says they will crush it, usually by making you run over it with your car! you also face the possibility of an on the spot fine & if the Gendarme is a bit bolshy even confiscation of your car & the only appeal is via the local Prefecture, who WILL back the local law & not you!