Quote from Brass:
Gun laws. Strict ones. With fierce penalties. As I understand it, the Second Amendment is in place to protect the citizenry from the government. That was then. This is now. Do you think if the government wants to take you out you can prevent it? As OBL found out, if the government wants to get you, you get got. So please, no alpha male rugged individualist claptrap. That would be step one in eliminating the collateral damage caused by the ridiculous cocktail of overabundant testosterone and the need for rugged self-expression.
Yes, thugs don't play by the rules. But no change comes without some interim pain. Eventually, and in due course, access and availability would become seriously restricted, either to certain people or in terms of certain weaponry outside of the most basic. In the meantime, and after a suitable period during which gun owners will have time to turn in their illegal weaponry, task forces could be deployed to confiscate weapons wherever they may be suspected of being held, along with making the appropriate arrests along the way. Did I mention stiff penalties?
That's how I would do it. But of course it would never get done that way. The "how" would at best be limited to eliminating certain forms of weaponry from the general public and restricting access to basic guns to people who must first pass a stringent background check along with any psychological profiling that may be required. At the person's full expense.
And what are the specific logistics of your "why?"