Would you go through the green channel at Heathrow having bought an expensive watch in Dubai?
Would you walk through the green channel at Heathrow wearing a 50k watch that you had bought in Bond St before going on holdiday in the USA without taking the paperwork with you?
If the luggage is your personal belongings flying into a French airfield from a Schengen country there would be no tax and nothing to declare. So I very much doubt that the douaniers would be interested unless they have received some sort of intelligence info or they are doing random.checks. But it is up to Swiss pilots to decide what they need to do. Personally, I would give them a call or send an email enquiry asking a direct question “does my overnight bag or that carried by my passengers count as baggage and need to be declared?”
Like I said above, that is another topic and it would be called “smuggling” 
If someone wants to start it, feel free.
In which case I’m not really sure what you.are saying. IMO the words “bagages are considered as merchandise” is perhaps not precise enough but for the life of me I cannot think of wording which would say what the douaniers might or might not be interested in. In legal terms that is. One would have to visit the actual arrêtes to see if this addendum on the Mulhouse declaration actually exists in that form. @Ibra may well have already done that.
BTW I believe this arrêtes or a similar wording is also included in the laws governing driving across the Swiss/French border. And the douaniers can stop a Swiss car crossing the border if they so wish. Normally they don’t unless they have prior intelligence information.
But let’s take a scenario which would have an effect on this wording and for which the French douaniers would certainly have an interest although it is not covered by the law quoted.
Both Portugal and the Netherlands have very much more relaxed drugs laws to France.
If one sticks rigidly to the wording posted from Mulhouse douaniers one should be able to fly from Portugal or the Netherlands (both being Schengen and EU) to any small airfield in France without any customs formalities. Do you really believe the douaniers would have no interest in such flights?
As I have written before the simplest thing if a pilot comes from Switzerland to a small airfield in France with his family ( whatever nationalities might make up that family) and s/he is worried about the ambiguity regarding personal luggage for a 2week stay would do well to contact the respective douaniers and put the question to them directly.
Peter wrote:
However we are still dealing with the “Luggage is considered as goods” clause – assuming it is a correct translation. It appears to undermine this entire concession.
I disagree. There could be several separate issues, but we normally see it as one single issue. For instance entering Norway from EU is described by the CAA in their VFR Norway.
From what I gather there is one issue to remember: you are the sole responsible for all of this. The main problem is, the laws and regulations are a tangled web of conditional exemptions and inclusions.
When looking into what the law (in Norway) actually say about informing customs (§ 2-1), it says three major things:
This is all about goods, and I’m sure the internal EU regulations are very similar (for internal EU stuff).
The next paragraph in the law (§ 2-2) is about the duties of the driver of the transporting vessel (land, sea or air) regarding the point of entry. It has nothing to do with goods at all. It’s all general terms, and include a similar clause about the department issuing regulations.
Of course, the department has issued regulations and lots of it. It is rather obvious that all this is mostly about actually transporting goods in the real sense, like a transport company or import/export company. But, in relation to § 2-2 there are separate and explicit regulations for private vessels in the regulations. And that’s the irritating part.
There is no logical reason for this discrimination, and I’m glad the EU has removed this nonsense. You could of course say that § 2-2 will give you a kind of “legal protection” from doing stupid things, or against the tangled web of conditional exemptions and inclusions and poorly defined terms. This is purely theoretical nonsense IMO. Why would you need that by air, and not on land or sea? Flying to Sweden I feel no issues in this regard.
Re France, friend of mine received these infos yesterday whilst trying to amend his ETA for his destination:
Bonjour,
Pour déposer votre préavis, vous devez utiliser le document en vigueur ci-joint “modèle de préavis de vol”, en heures locales, en complétant toutes les rubriques.
Dans un souci de bonne gestion et de traçabilité, une uniformité des préavis de vol est demandée. Ce préavis de vol est une formalité douanière obligatoire qui sera transmis aux brigades de Douane territorialement compétentes.
Pour toute modification de voyage, il vous suffit de nous envoyer le document rectifié sous le même formalisme en respectant le délai imposé par la réglementation.
Important : noter en objet de votre mail : l’aéroport d’arrivée – date d’arrivée – immatriculation de l’avion et aéroport de départ – pays de provenance )
Cordialement,
Centre Opérationnel Douanier Terrestre de Lyon
6 rue Charles Biennier – Lyon 69002
Tél. 09 70 27 30 28 – Fax. 04 72 82 12 0
With the “Informations devant figurer sur préavis vol”
… and the “Fiche pratique 1 vols transfrontaliers”
In which point #3 underlines Swiss specifics 
That is simply outdated information from the French authorities. If you look at that “AIU” list, which is available for download from the EU Commission, there are only official customs airports mentioned from all EU-member states. According to 2020/877 regulation, you don’t have to depart or land at those airports anymore, if you don’t have cargo to import or export.
Other EU regulations define what “cargo” or “merchandise” is, so this is IMHO also not something French customs offices can define by themselves.
This is all really a very bad joke. It’s time for the EU Commission to intervene.
At least outbound, you can file an FPL to an EU aerodrome close to the Swiss border, and then just divert.
List_of_International_Union_Airports_pdf local copy.
I think that list may be out of date IIRC there are 1 or 2 at least eg LFBN Niort not included there.
There is a long history of EU lists of ports of entry being out of date. Especially in France.
There is really no way to be sure other than AIP + NOTAMs + ask the airport.
