In reality radar detector violations are not rigidly enforced in the US - even the conservative states that do not allow their use.
I was surprised by Robbo, Smokie and others revelations about new types of fixed speed traps that photograph no. plates and measure over specific distances for ave speed. It would be great if the plod applied as much creativity to catching criminals and preventing the ever rising tsunami of illegal immigrants into UK.
Here in US, Highway speed enforcement (as opposed to urban, which is a different argument altogether) is purely a revenue generation strategy - and the Cops treat it as such - no lectures about death and destruction - "Where's the fire, sonny?" just book 'em and onto the next one. They don't give a sh*t about radar detectors, even in DC, where they are fabled to have zero tolerance.
In France, I would imagine the nifty Fazer would be more appropriate. This is a radar/laser jammer, rather than a detector. It corrupts radar and laser patterns and again is legal in most states here. Good bit is that you can mount it discretely - even between the radiator and front grille, rendering it all but invisible to the filth and will also confuse an 'instant-on'.
The manufacturer offers to pay speeding fines of users if caught, while using a Fazer (can't help feeling there would be a bit of small-print attached to that offer, however).
Downside is that it is only forward facing - no good if Smokey Bear is sneaking up behind you. Fazer costs around $350.00