There are a few crazy gun grabbing states. CA, CT, MD, MA, NY, IL.
Then there are even crazier cities that could pull this as well.
The media would get on board with the commies and could pull this off. They are obsessed with private sales and the so-called gun show loophole. Tracing back a gun used in a crime to a private seller or dealer means that more gun owners and gun dealers will be caught up in their web. That’s why cash bans and any seller/dealer registries need to be aggressively identifies and opposed.
The key term is “traceable list”. There are a lot of people who would accept having to do a background check on a private sale as long as no records are kept. As soon as you add “ maintain a list”, that support, even among many gun control advocates, drops drastically.