I’m in no way saying that folk should break the law… merely saying that there is obviously a great deal of misunderstanding about what the law says and how the law is interpreted…
(I used to have regular friendly meetings with our gendarmes…sadly not the case at the moment… but when/if I get the chance, I’ll ask their thoughts on this… )
One simple response @Stella - ignorance of the law is not an excuse 
As I said, whilst a Gendarme might choose to overlook the issue because of a lack of clarity, it is unlikely that the Douanes will - it’s their job to collect taxes and indirect duty and they perform their function very effectively.
The folk I shall be talking to won’t pull their punches !
but it will probably be not until next year, so a bit late for this current discussion.
Friends of ours rented here for a year so reg car here.
Just gone back to UK and had great difficulty in finding
Uk insurance cos of French plates, so eventually did it on chassis number, so he could go up north 350miles driving an insured car.
However now having to leave car on his drive as he was told correctly that as he is now a uk resident again…rental property handed back, so no French address it would be illegal to drive his still French reg car in uk until re-reg. …risk of fine and much hassle if a traffic cop stopped him and became jobsworth
I have a very friendly former gendarme neighbour (not completely retired, he has been called back for occasional duty) who I could ask next time I see him, but it would be only an opinion and, as I saw with the ridiculous traffic police in Cornwall some years back who thought that nobody could drive in England without a British licence, such worthies can get it mind blowingly wrong.
I’ve given up trawling through car stuff for today… virtually everything talks as if the Driver is the Owner… and this is not the case according to the OP.
There is this link, which does talk about a French Person driving the “foreign” car owned/registered by a foreign resident…
and thereon it worries about insurance…
Interesting article, Stella. It would be helpful if it linked to the actual laws rather than explain their understanding.
I wonder how this applies to me? I’m a French resident with vehicles here on French plates with French insurance. My licence is still UK as I don’t meet the exchange criteria.
Members of my UK-based family visit me here from time to time, and my insurers have confirmed that they are all covered to drive my cars subject to minimums of age and experience.
I am a named driver on a UK-resident daughter’s policy. Her insurers know that I am a French resident with a UK licence.
My understanding is that I am allowed to drive her car on UK roads when I visit them. I must admit that I had also assumed that I’d be legal driving it in France too when they visit me but now I’m wondering…
Gosh David, scary incident 
It certainly was Lily, all I could see was those 3 great big wheels heading towards me and I squeezed as far as I could to the edge of the road, but the edge gave way and we were slammed into the rock face. This did over €2,000 worth of damage including 2 smashed windows at the rear. The swearing was because the angle of the car was so great that the door wouldn’t stay open and I was giggling hysterically at the silliness of it, hence the language. 
I only got out because I turned on my side and pushed with my feet on the centre console while that bike rider held the door open for me. The 2 Boxers in the back were totally unconcerned, of course, no swearing from them. 
Insurers may insure a person for a car but it doesn’t necessarily make it legal for them to drive it!
Visitors to France can drive a French registered car and visitors to the UK can drive a UK registered car.
A French resident taking a UK registered car into France to re-register has to declare it on entry and has one month to start the transfer. Legally it cannot be driven so should be on a trailer.
Douanes no longer deal with quittus fiscale which now handled by the Prefectures.
The friend should have driven the car into the UK on the French insurance that covered the French registration.
UK insurers can only insure UK registered cars but can be insure by chassis number pending a re-registration.
b33jay is correct in that bringing a UK car to France if you are resident here you must start the re registration process within one month. You do not have to declare it to customs on entry. You can still drive it if it is road legal. Normally it is the Revenue, main tax office that deals with the fiscal side. Un étranger qui s'installe en France doit-il y faire immatriculer son véhicule ? | service-public.fr. En tant que résident français, votre véhicule doit impérativement être immatriculé et assuré en France . Ce qui signifie que votre voiture ne doit surtout pas rester pendant plus de 6 mois à l’ étranger .Jan 8, 2019
I have now found a reference to driving a foreign registered car in France (or any country) and it’s related to the Vienna Convention.
French Decree 77-1040 of 1977.
The Vienna Convention provides for the authorization of circulation of vehicles registered abroad . There are no different rules for cars registered in the EU or outside. However, conditions must be met to be able to benefit from this right:
The owner must be a person who has his main residence outside the country visited.
Therefore a French resident cannot drive a car registered in another country.
perhaps a slight misunderstanding… since according to the OP
the Owner does have main residence outside France (ie in UK)
It is the French Resident (NOT the Owner) who seeks to borrow the UK car and drive to France and then back to UK…
Very useful, @b33jay ,
But I don’t understand how B follows from A. I did start to go through that decree from 1977 but I must confess that I did not get to the end…
This is from Car registration in another EU country - Your Europe
" If you are temporarily driving around in your new EU country, you should not lend or rent your car (still registered in another EU country) to a resident of that EU country. This is because the person could become subject to a fine. You may, however, lend your car to visiting friends or family members as long as they do not have their residence in that EU country.
You may be fined:
You can check the exact rules that apply to car registration in the country you are moving to on the websites of the national authorities:"
But to muddy the waters it also adds “The information on this page does not apply to UK nationals residing in the EU and EU nationals residing in the UK. National rules are applicable in these cases.”
Muddy waters…
I’m thinking that the confusion is getting worse… and not better…
Problem was that he no longer had valid insurance having given up the French property where had lived when he took it out. No longer now being a French meant he couldn’t get insurance…so he would have been driving without insurance on a French plated car. It was v difficult to get uk insurance on a French plated car, and in addition actually driving it in the UK as a resident is illegal
…quite so my friend is now in the country of residence with a foreign (French ) car so its on his drive until after DVLA complete the re registration and new reg’ plates arrive.
I have recently researched this. I am now resident in France but for the time being my wife’s primary residence is UK. According to the conversation I had with an official at the DVLA I, as a French resident, cannot legally register a car in the UK. So my car is now registered in France. I still spend around 5 months a year in the UK, I drive my French registered car there quite legally. Conversely my wife, not a French resident, must register her car in the UK. She drives it to and from France quite legally since she spends around 5 months of the year (within the constraints of the 90/180 rule) here. We are both insured as named drivers on each others cars and can legally drive those cars in either country with the permission of the registered owner. So there is a letter in each car giving permission for the other partner to drive it. So if your husband is resident in France he cannot own a car registered in the UK. But he can drive a UK registered car provided he is insured and has the permission of the owner, and he can do so in any country that the car is insured for. Sorry, no paper reference for this, but you can contact DVLA and check this with them.