Seems like you'd want to subpoena source code or gmail history or something like that. Not much interesting in an office these days.
At this point a nuclear power like France has no issue with using covert violence to produce compliance from Musk and he must know it.
These people have proven themselves to be existential threats to French security and France will do whatever they feel is necessary to neutralize that threat.
Musk is free to ignore French rule of law if he wants to risk being involved in an airplane accident that will have rumours and conspiracies swirling around it long after he’s dead and his body is strewn all over the ocean somewhere.
It's just that the West has avoided to do that to each other because they were all essentially allied until recently and because the political implications were deemed too severe.
I don't think however France has anything to win by doing it or has any interest whatsoever and I doubt there's a legal framework the French government can or want to exploit to conduct something like that legally (like calling something an emergency situation or a terrorist group, for example).