It is my belief that with the Red Flag laws in effect, and those two calls regarding Suicide threats and the murder threats, the police have all the authority they need to Flag him and prevent him from passing a background check.
They had enough information and authority to take his knives, how do they then not have the authority to prevent him from buying a gun?
If the "kid" then wants to appeal the constraint he can take his case to a judge.
Exactly...