Well, they might be able to go against the domain registrars and possibly cloud providers that also operate in the french market. But those companies probably have a bigger expensive legal team, while quadnine is just a little non-profit.
And what is your proposed solution to that? It takes minutes to move a service to a different IP, this is a gigantic whack a mole
If france wants to institute their own great firewall then they should just do that rather than engaging in twisted extra-national half measures that make liability confusing for everyone.