I would be surprised if there is not a process for recognizing Dan grades earned outside France. I am sure it involves some hoop jumping and lots of paper work, but I am confident the process is there.
Yes that is true, but it really boils down to how much bending over backwards you are ready to do to get it.
That being said, I do not think that the fact that the government wanting to regulate titles and teaching credentials is necessarily a bad thing. I have seen too many dangerous things being taught to children in my time abroad by unqualified, so-called Sensei.
Also, let's not forget that Aikidoka in France are 70 000 strong primarily thanks to the generous help of the government in terms of funding and facilities. If really people wanted to get rid of the state's influence, they probably could, but it means that they would have to become real pros and loose benefits from the government's generosity. Tuitions would also get a lot more expensive as a result.
So I think that given the context, Christian Tissier's response is exemplary, but as far as the situation is concerned, things are not as simple as it seems.