Registering a fire arm is considered self-incrimination via Convicted Felons

Convicted Felons Do Not Have to Register Their Firearms

U.S. Supreme Court’s 1968 Haynes v. U.S. decision:  Haynes, a convicted
felon, was convicted of unlawful possession of an unregistered
short-barreled shotgun.   He argued that for a convicted felon to
register a gun was effectively an announcement to the government that he
was breaking the law and that registration violated his Fifth Amendment
protection against self-incrimination.  The court, by a 7-1 margin,
agreed, concluding: “We hold that a proper claim of the constitutional
privilege against self-incrimination provides a full defense to
prosecutions either for failure to register a firearm or for possession
of an unregistered firearm.” (Summary from American Rifleman, March
2000, page 20)

So, when gun registration schemes are announced, be aware that only
lawful gun owners will be required to register their firearms.  Unlawful
owners are exempted from registration laws due to their constitutional
protection against self-incrimination.