A statement of the law from the AA: http://www.theaa.com/motoring_advice/overseas/radar-detectors-in-france.html and advice from Garmin: https://support.garmin.com/support/searchSupport/case.faces?caseId={1a0e3820-3be3-11e1-613e-000000000000}
Check whether this in force yet . I have a feeling it's like the law about having a breathalyser in the car, which was passed but then suspended in operation.
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