My understanding is Haynes is still good law and felons do not have to register guns.
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.