It's very pleasing and inspiring to see all the many wonderful, creative ideas being generated here and elsewhere for how we can institute a rational set of gun policies that protect all Americans - not just the extremist minority who value their impunity over the lives of their fellow citizens and the security of our communities. Below are some of the best ideas I've seen, covering both the obvious and some very unconventional but highly insightful proposals that I hope are officially explored.
In no particular order...
1. Ban weapons whose only practical purpose is waging war - i.e., those that produce maximum body count in minimum time. There is no legitimate civilian application for such weapons, and no practical scenario where it would ever be justified even in the wildest fantasies of paranoid gun nuttery. Our government possesses enough nuclear weapons to destroy human civilization, so the possibility of territorial conquest by a foreign power is zero, as is the possibility of militarily defeating a tyrannical domestic regime without having enough political and logistical support from the public that privately-armed groups would be virtually irrelevant and probably insubordinate to the higher-level rebel commanders (as George Washington ended up having to contend with in the Whiskey Rebellion).
2. The President calls up the "unorganized militia" (i.e., all gun owners) and subjects them to military-style (but not actual military) discipline, testing, and monitoring. Not only would this not violate the 2nd Amendment, but in fact the Constitution explicitly mandates it as the purpose of guaranteeing the right to bear arms. We would see what kind of hypocrites populate the alleged 2nd Amendment crowd if/when the President did this - who only has guns because they see them as toys with no responsibilities attached; who thinks guns are their way to exempt themselves from legal authority, etc. And he doesn't have to do anything with them once he calls them up, since the national emergency that justifies it is the very lack of discipline and oversight among them that calling them up would rectify. Basically, this would mean everyone in perpetuity who purchases a gun subjects themselves to this rigor - they would not be denied a gun, but they also cannot shirk the requirements without being brought up on charges equivalent to AWOL or desertion. (Credit: Plisko)
3. Hold gun owners legally accountable for whatever happens with their guns (in addition to whoever uses them, obviously), no matter what. Your gun was stolen? Well, too bad you didn't take adequate precautions to prevent that, because now you're going to be charged with negligent homicide if a bullet from that gun ends up in a dead body. And if you knowingly fail to report it stolen to avoid just such accountability, it's no longer mere criminal negligence - it's accessory to whatever crime ends up being committed with the weapon. Of course, to be fair, there would be a statute of limitations - so you're not going to be arrested because a gun stolen say 10 years ago ends up being used in a crime. The ways to secure guns are well-known and proven to allow timely access when necessary, so there are simply no excuses at all.
4. Mandate that all civilian firearms be dyed hot pink both for easier identification and to mess with the minds of gun nuts, who are overwhelmingly misogynistic and homophobic. I would add the idea that guns should be required to have certain form factors that make them look "feminine," just to more extensively fuck with people whose motives for having guns are juvenile or psychotic and should thus be dissuaded from interest without denying their rights. You have a right to bear arms, but there is no Constitutional right for guns to look a certain way so the people possessing them will feel cool or manly about doing it. Anyone responsible enough to safely wield a gun and serious about wanting one should be able to handle looking ridiculous holding them. Hell, you could even sell it as an added part of the weapon's effectiveness - a criminal would be so startled by how ludicrous you look, their response time would be reduced. (Credit: Gary in NY)
5. Ammo tax. An idea that's been floating around for a while is to heavily tax ammunition so that rampages would be far less likely - e.g., if a single bullet costs $50. Any legitimate concerns about hampering people's ability to train with their weapons could be solved by exempting ammo provided at licensed and regulated gun ranges that is uniquely stamped on a microscopic level and never leaves the premises. If any does leave the premises and ends up being used in a crime, all sorts of audits, inspections, penalties, and possible criminal investigations of that gun range and its owners and employees could follow. So, basically, you can train all you want at these ranges, but as far as what you personally own, you can defend yourself and nothing more - there is no right to rampage.
6. Ban high-capacity magazines. Same rationale as #5 - there is no hunting or self-defense justification for such magazines, and no plausible scenario where having them easily available in civilian life serves a security purpose. So far they've killed countless people in murder and haven't proved crucial in saving a single life outside of active war zones. Sold to civilians, they are nothing more than tools of murder that endanger and terrorize law-abiding citizens without giving them back any practical ability to defend themselves - if they unload on an attacker in kind with similar firepower, they just multiply the chaos and danger to those around them. As the 2nd Amendment explicitly says the purpose of the right to bear arms is the security of a free state, any weapon/ammunition that does the opposite when allowed to proliferate unregulated must be brought under strict control (e.g., armor-piercing rounds, flechettes, etc.) to be in compliance with the Constitution.
7. Delayed reload. Impose requirements that reload mechanisms must involve a nontrivial delay that could not be easily circumvented by the user without compromising the ability of the weapon to fire. If you find yourself in a situation where you've unloaded your gun and are still in immediate danger, most likely you are the one trying to commit a crime - or at least involved in crime enough that someone with a bit of firepower really wants you dead. And even if you're not a crook, you've endangered the lives of bystanders by being such a reckless, lousy shot. I think most Americans are willing to take the risk that someday they might be pursued by an unstoppable Terminator - they don't feel like that's a realistic fear. Because it's not realistic. So, delayed reload: Built-in opportunity for people to jump a maniac on a rampage.
8. Hold gun manufacturers personally responsible for designing and selling products specifically optimized for criminal homicide, if not mass murder. I don't care how many times such attempts at liability or prosecution would fail in court before they finally stick - this is simply a moral imperative, and these people need to feel the heat every minute of every day from every possible angle.
9. Federal ban on concealed firearms. Unless you have a good reason to believe you personally are being targeted - like, if you're in the witness protection program, or are being stalked by a violent ex who you think is capable of murder, etc. - there is just no legitimate purpose to carrying concealed firearms. Fear and the desire to create fear in others is not how a free society makes law, and it obviously does not make people safer or Dallas would be as safe as Tokyo. Under the vast majority of circumstances, the only reason to hide a weapon is because you obtained it illegally and/or intend to use it in a crime. That obviously violates the "security of a free state" the 2nd Amendment speaks of.
All of this creates a multi-tiered system of accountability and murder prevention while still maintaining the right to bear arms. And on a tangential but not wholly unrelated subject, we can open up space in the jails for the violent people and criminally irresponsible death fetishists by ending the War on Drugs. If someone wants to have fun and doesn't hurt anyone or do themselves enough damage to see them as suicidal, leave them the hell alone and mind your own damn business. If someone does OD or endanger others with their drug use, send them to rehab. And someone who won't accept even the most basic legal and Constitutional responsibilities of gun ownership because they see them as toys or macho statements, endangering however many lives, that's who you lock up. The people who take upon themselves the power of an army but are so reckless they don't secure their guns from theft or accident, that's who you lock up. And people in suits who make a hundred million dollars a year selling products whose only function is murder, that's who you lock up. See how fast the actual street criminals at the bottom of the market run out of weapons supply when you hold the people higher up the chain accountable.
12:55 PM PT: I won't be able to answer comments until later this evening, so please excuse my not responding immediately.