Felons, prior to GCA 68 had no federal prohibition on owning/possessing purchasing firearms to my knowledge. Now they do, therefore Haynes is pretty much of no value. Not telling a LEO that you ( a felon) have a firearm or ammo still is protected by the 5th, them proving it will earn you up to $10k/10 yrs in the federal house.
Haynes is still good law. The issue is providing information that is an admission of a crime. In other words mandatory registration for a felon or other where it would admit to a crime. It’s a sick irony but because of Haynes and the 5th Amendment Felons do not have to register guns. This is not to say they can escape taxes. That’s a different issue. But, firearm registration laws completely miss the claimed population target and instead apply only to the law abiding.