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.
Why not? After all, that's in vogue today. Trump is ignoring all the international agreements and rules, so why should others follow them?