Some informations :
- the closing is done by the administration and thus is using administrative reasons: the non respect of administrative regulations. The may be or there may not be a penal and civil lawsuits to follow, but those will take longer. There may also be a suit against the administration contesting the decision (*). I'm not aware of anything taking place.
- the club closed isn't one of the Mediterranean coast, and no local entities were involved in those dives.
- if the rumors (I'm from the area) are right, they were diving a known wreck (so that's not a less deep dive gone very wrong, the depth was planned), on air, with 15l tanks and no additional deco... that was daring by any standards, even French one.
(*) they will perhaps try to argue that the regulations didn't apply to them as, although all but one were members of the clubs and most with an official position there, they weren't acting as such but only as a group of friends and there is no regulations which apply when a group of friends dive together. That may save the club from the administrative consequences, this will be of no help to the involved people if there are civil and penal one.