I've lost an inordinate number of friends to lunatics with guns. I am a gun owner, a liberal, and pro gun regulation. So I dig in to this quagmire with some regularity, searching for a way through to the other side. (The "other side" being some practical, legal way to regulate gun sales, training, and insurance, modeled kinda on car ownership.)
There are two key stumbling blocks:
1. The Individual Mandate. The Supreme Court has ruled that an individual has the right to own any gun without restriction. That is the law of the land, currently. The only way to change that is to have the Supreme Court hear a case that shows the Individual Mandate to be in contravention of the Constitutional rights of Americans.
I have noodled this quite a bit, but I cannot conceive of a court case where an individual's rights would supersede the rights of all Americans. (AKA - "The individual mandate so egregiously wrongs this individual that we are going to remove this Constitutional right from all other Americans.")
That's just the reality of the situation. I do not currently think there is a case that could be brought before the Supreme Court that would cause them to backtrack on the Individual Mandate.
2. Reduce the number of guns in the wild. If we can't force people to give up their guns because of the Individual Mandate, then maybe we can incentivize people to turn in their unwanted guns, and make the transfer of ownership exquisitely difficult, and provided by few service providers.
Take the example of a dealer in antiquities.
They need to know the provenance of the piece they are selling. A full and reliable paper trail of ownership, going back as far as possible, so they know the object in question was not stolen from a museum, looted from a heritage site, a counterfeit, etc.
Every item an antiquarian sells is highly scrutinized by multiple reliable sources, whose reputation is on the line, and who takes great pride in the work they do. There aren't many people that can look at an Egyptian figurine and determine where it came from, what it is, the chain of custody from when the item was discovered, all the way to the item sitting in the assessor's hands.
Drawing the Antiquarian parallel to gun ownership: If I want to sell a gun, I need to register my desire to sell it. I have to provide as complete of a chain of ownership as I can. I need to provide a currently valid certificate that the federal government is not looking for this weapon in connection to any crime. Etc.
To sell the weapon, I have to turn it over to an authorized dealer (the antiquarian-like professional described above), who certifies the transfer from owner to owner, and takes a small percentage of the sale price for their service commission, thereby incentivizing them also to sell it at the highest price possible.
Along with some sort of federal buy-back program, targeted at gathering up the shittiest of the 250m+ guns off the market, this could, over time, be a Constitutionally-resilient way to begin to deal with the gun problem we have in the USA.
... yeah, it's still just a germ of an idea, but I'm teasing out the details, and working on how this could be implemented, practically speaking. (There's a good model for this here in Seattle right now. A lot of marijuana shops opened up when things got legalized. But as the business reality of regulation, taxes, banking issues, and supply chain management become more refined, the less-professionally-run pot shops are going out of business. This leaves us with higher quality shops, meeting strict regulations, and operating in a very professional manner. I can see the same thing happening with gun shops, if my gun sales idea ever goes into effect: consolidation of many small businesses into larger, more professionally run ones. Dodgy edge-case operators getting out of the business entirely. And the Gun Show loophole finally being closed for good.)
Eh. It's an interesting puzzle to try to piece together. And a worthy goal, in the end.