Add microchip intelligence to all firearms for sale to the public, which will preclude their firing by anyone other than their registered owners, or anywhere identified by GPS coordinates as inappropriate locations.
Provide funds for the US Government (ATF) to sponsor technical development and subsidies to gun manufacturers for implementation.
Require all registered guns be returned for modification/replacement at government expense. Exemptions for "classic" or "heirloom" weapons granted on case by case bases, but to include ballistics registration for all such weapons granted exemption.
Why is this important?
Convert pistols and rifles from their ancient mechanical/chemical operation to electro-mechanical/chemical operation, introducing safeguards which will prevent their unauthorized or inappropriate firing.