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.
Seriously, every powerful state engages in state terrorism from time to time because they can, and the embarrassment of discovery is weighed against the benefit of eliminating a problem. France is no exception : https://en.wikipedia.org/wiki/Sinking_of_the_Rainbow_Warrior