In reference to the patent: US6194720
Is that patent valid in France?
US Patent grants are not directly enforceable worldwide. On the page you link to, you'll see an Espacenet link - that is a link to the EPO version of the patent, which will have the same description but usually a different set of claims. On that Espacenet page, look for the Legal Status and Patent Family links for foreign applications. Within the patent family I only see a single document - the US Patent grant US6194720 (B1), so it appears that no WIPO (worldwide, international) or EPO (European) application was filed. This means that the patent is only enforceable in the US.