So I'm assuming a theoretical discussion that includes an assumption that there will be laws restricting possession and that all we are talking about here is how could this be accomplished. I'm not discussing what is or is not permitted by the 2a, nor what it could be perverted into by the dishonest or incompetent.
I posted this not long ago in another thread;
As with the development of any solution I welcome constructive criticism, comments on the flaws and how to fix them.
There is absolutely no way for a "citizen database" to work because you're ignoring the concept of federalism.
Most people do not directly deal with the Federal government outside of Federal income tax, college loans/FAFSA, or certain Federal benefits/programs like the VA, SNAP, etc. Most people's interaction with government involves the state government. Arrested? Probably arrested by local government and prosecuted by the state. If you're getting arrested by the Feds, you're having a bad time. Who prosecutes most crimes that render people ineligible to buy guns? States - domestic charges, most felonies (drug charges, felony assault, B&E, sexual assault, etc.).
Let me put it to you this way. I pay taxes to my fire district, my town, my state, and the Feds. I don't think you understand how disconnected different parts of the government are.
Here's an example. If someone's arrested for operating on a suspended driver's license in RI, there's literally no communication between the actual criminal justice system prosecuting and defending the crime and the Division of Motor Vehicles who control motor vehicle licensing. I met one client this summer while I was interning for the public defender who is going through a Kafka-esque nightmare of seven or more years because of bureaucratic failure to communicate.
Now, with guns, its a little easier in theory because you're only dealing with one Federal agency - the ATF. But the ATF gets all its info from the states unless someone's ticked off the Feds. And what the ATF wants is control over the system. Creating a user interface that allows people to NICS check themselves goes against the ATF's intent. In theory, the ATF can totally shut down and stop processing NICS checks, halting gun sales.