Using any kind of signal jammer is a crime in the UK. It wouldn't surprise me for it to be a crime in France.<p>See <a href="https://www.ofcom.org.uk/spectrum/interference-enforcement/spectrum-offences/jammers" rel="nofollow">https://www.ofcom.org.uk/spectrum/interference-enforcement/s...</a> for example<p>"It is a crime to use any apparatus, including jammers, for the purposes of deliberately interfering with wireless telegraphy (radio communications) in the UK. The maximum penalty is two years’ imprisonment and/or an unlimited fine. See section 68 of the Wireless Telegraphy Act 2006."<p>Ofcom is the UK's communications regulator.