Interesting responses indeed :wink :eek
The rental company Sixt charged a 20 or 25 euro fee directly to my credit card for each supposed infraction. This is for them passing on my mailing address to the authority that wants the $. It is my understanding that the authority cannot force the rental company to collect or charge my card on their behalf.
Hence the question: what recourse does the authority have?
Read your rental agreement.
Typically, the fine print says you agree to let them use the credit card on file to pay fines.
The administrative fee is only the first shot.
You have a chance to pay the fine yourself. If you don't pay, the authorities may go back to the car rental agency and ask for payment of the fine and the late penalties, which can escalate rapidly.
You may get lucky, but most European countries are quite skilled at extracting money.
Maybe some of our friends in Europe can weigh in on the joy of fines that are assessed based on income. In Germany, the maximum fine a judge can impose is capped at about $12m US, fluctuating with the exchange rate of course. Switzerland is only about $1m. Don't know about France.