A subsequent upsurge in gun crime by gang members, or a lack of diminution of same should result in an announcement that the Authorities were not diligent enough in their confications. SWAT teams will then raid a series of Citizens who are known to still have guns or the police will bring their own evidence to selected citizens' homes.
At least that is what they will probably say.
Because the DemoSocialistMarxistLeftistLib's are all about telling the sheeple what they think they want to hear.