Let's say you're a convicted felon and you own a firearm. Let's also say the state you live in requires all firearms to be registered with the state.
The US Supreme Court ruled in Haynes v. United States, 390 U.S. 85 (1968) that you, in this scenario, would basically be exempt from the law requiring you to register as registering the firearm would violate your 5th Amendment right to self incrimination.
You see, as a felon you're not allowed to own a firearm. If you do, in fact, own one, and you register it, you're incriminating yourself. The act of registering the firearm incriminates you in the crime of owning a firearm. As the 5th Amendment provides you can't be forced to incriminate yourself in a crime, you can't be required to register your firearm.
Nice little loophole, isn't it?
