You know, I had a veritable epiphany about this problem this morning. Shows what a good cup of coffee can do for an aching mind. Anyway...
Somewthing that apparently has not been tried is a much higher level. How about this?
Contact the Trade Attache at the French Consulate. Explain that you have been victimized by someone who purports to be a French policeman. Give the specifics. Explain that you belong to a loose knit trade organization that sports over 70,000 members and even has a European branch. As what help the Consulate can offer because one crooked French cop shouldn't give all French businessmen a bad name. Appeal to the famous Gallic pride, arrogance and sense of honor.
Heck, everything else has been tried. If Plomian is a cop and the chief gets an inquiry from their State Dept, Oliver's chesnuts may get roasted in an open fire.
The only thing lost is time and the phone call.
Gene