We do not block IP traffic from known Turkish ISP ranges. The customer (the political group) receives all sorts of dire legal warnings and threats that what they publish is contrary to Turkish law.
None of our other hosting platforms are configured to block any traffic to/from Turkish IP ranges. We have no business presence or financial involvement with anything domestically in Turkey. Am I subject to Turkish jurisdiction? I don't think so.
But by what you wrote, I am providing services in Turkey.
Could Turkish intelligence link me to the company if they spent significant resources researching the hosting company that provides services to their political enemies? Probably. Do I have any personal plans to take a vacation in Turkey any time soon, or a pressing need to visit Turkey? No.
I am pretty sure we also have someone, somewhere hosting something that insults the King of Thailand, so I suppose that's a risk too.
If I operate a bookstore physically in switzerland and a few of the books I sell are illegal in france I'm not required to check passports or whatever, am I? I can just sell books to whoever (subject to swiss law) and if a french national illegally imports one to france that's a problem for customs or the local police or whoever (analogously the french ISPs) to deal with. Not me, the swiss bookstore operator.
Now consider if I were handing out pamphlets for free rather than selling anything. At that point I'm arguably not even doing business because no money has changed hands.
I realize that the current legal reality might be that quad9 needs to block french users in practice but the entire thing is a farce if you stop and think about it.
In the Quad9 people’s case, defying French law and still doing operating the services under French jurisdiction might work out just fine for as long as (1) holds true, but it doesn’t take a consorted effort of research to change that. It could just be that some leaked piece of information eventually surfaces. It could be a tweet posted by someone else. And I don’t know how many people work for that organization, or might do so in the future, but it seems like a bad move to make a decision on their behalf to paint a target on all their backs.
Also, France being part of the EU makes being an enemy of the state there seem even more unwise for anyone who might want to have associations in any other EU country.
I personally would do exactly what they are doing: if French people want a government that respects free speech, they had better elect one themselves. I wouldn’t become a martyr to that cause - it wouldn’t help anyway.
But even being based in Switzerland I believe there’s some inter-countries agreements, so it would not be practical.
GP's point is that whenever you sell or offer something to users in U, you have to abide by U's laws in doing so - no matter whether you did that all while sitting at your desk in country C.
Whether or not enforcement or liability is realistic is up to the relationship between U and C I guess - my guess is France and Switzerland are on pretty good terms.
This is not exactly your focus, but this means that it can be possible for there to be a set of laws in U, such that an action is required and illegal if not present, but that this same action is illegal in C...
I.e., the predication is both meaningless and pointless, unless the supposition is that the laws of U don't hold - if C extradites a citizen of U over said action, is then U's law not supreme?
It is about as enforceable as "don't read letters written by redheaded people": it'll never be airtight, and it'll always have a huge amount of false positives.
The only possible "solution" is to ban all open devices from the internet, mandate a DRM-style "trust zone", have the device do mTLS, and embed a realtime DNA sequencer in every device.
Realistically, Switzerland and France have a relationship; treaties, etc. Quad9 has to comply with Swiss law, and they probably hope that making reasonable good-faith moves to block French users will cause Swiss courts (if it comes down to that) to see them as the more sympathetic party.
Regardless of what analogy you use, the point is that the company isn't in France, it's in Switzerland. It doesn't make sense for it to have to do anything to comply with French law, even if it's interacting with someone who happens to be in France.
WRT your second paragraph, I think I addressed it already in my second paragraph.
The Principality of Sealand*
* until the UK or French navy shows up