Nanoha comes from a ninja family. A ninja ASSASSIN BODYGUARD family, one would think they would helo out with killing majins.
Her family don't work for TSAB and are considered civilians.
HIGHLY dangerous civilians
That presumes the Toraha canon is also canonical in (this particular) Nanoha timeline. Let me remind you that the Toraha!Shirou has died on the job some time before Nanoha turned 9, but is alive in the TOS continuity, which is an argument against him being a ninja bodyguard there, too.
He was a ninja in the Nanoha timeline too, he just survived. Him being hospitalized is a big part of Nanoha's backstory in season 1/the first movie. There are implications that the other things are canon in this timeline too, though Arisa is probably not a ghost.