[hga]

All 20th Century gun confiscations I can think of, aside from the Chinese Communists' rifle tax system, were preceded by registration. Nazi Germany most infamously, and in occupied territories like the Netherlands failure to produce yours would result in your entire family being summarily shot in the village square. But also Cuba after Castro took power, or less dire (so far), the U.K. bit by bit. Or closer to home, California, after the AG decided that SKSes were banned after all.

Last time I checked, which was decades ago, the national ACLU, which has no respect for the 2nd Amendment at all, did have such a 4th Amendment objection.