Having said that, it is fun to think about how hard obtaining guardianship in this situation would have probably been for most people. Vivio is such an anomaly after all. Nanoha was certainly in the right place at the right time, but it probably pays to have her connections and background as well!
That, and I doubt anybody in the Mid-Childa administration would want to anger the "White Devil" of the TSAB by refusing her to form her ideal family. XD
Yep, cause the last thing anyone wants to be on is the wrong end of a Starlight Breaker