I have no problem with something like this.

Have a shooter's license, analogous to a driver's license. You must have one in order to buy or possess guns or ammo. You take a course on gun safety, pass a written (or possibly oral) exam, and perform a satisfactory demonstration test. The license is basically a baby CCL. It comes in degrees, with special endorsements for things like scary-looking guns that can shoot a lot of bullets. It is linked to the criminal database. Commit a violent crime, and your ticket is suspended or pulled altogether depending on the severity.

Law enforcement sees you out with a gun, they can ask for your license. You don't have one, and you go to jail. That allows some pre-emptive action on the part of LEOs. This could go a long way toward cleaning up things like gang shootings.