We are not in disagreement. The issue was only registration of guns and admitting under oath to committing a crime on an official form. As it stands right now firearm registration laws only apply to the law abiding and not to the felons that the gun registration laws were presented as preventing from purchasing firearms.
With respect to the original topic. The same argument applies. They cannot compel a person to admit to a crime - illegal use of drugs - on a form.
Yes, look at the 4473. It asks all of those questions (fugitive, illegal drug use, illegal alien, mental defective, etc) and to not answer or answer wrongly DQs from firearm purchase as a prohibited person. And is a crime which while not often prosecuted by the administration (s), is a federal felony that is upheld by the courts.
Note: I do not believe that permanent disenfranchisement of civil rights is constitutional or even necessary.