Gear up landing, when does the FAA get involved?

[Rene]

Depends. A number of states and municipalities have local laws permitting aircraft accident investigations and the federal rules note this. For example, Ohio has such laws. However, no other agency other than the NTSB are permitted to participate in any probable cause determinations.

I was merely responding to the quote.

Why in the world would the police be involved in a gear up? Some stole the landing gear? Or maybe the landing gear switch?

And pointing out that theft from / vandalism of a FAA registered aircraft is a federal crime.