All handguns are also registered with the state.
I know first hand of numerous instances where individuals passed away, and the firearms were confiscate from the grieving family.
I had forgotten about that one, thanks for reminding me, as it is one that I should have remembered. Though I don't think its exactly what the OP is looking for.
New York State has required all handguns, and their owners, to be "registered" in their permit system. And, it has been their law since at least the 1960s though I can't speak for earlier. And, it is an actual registration system, as your handguns are listed on the permit, by make, caliber, barrel length and serial number. The guns listed on your permit, and ONLY the guns listed on your permit are the ones you may legally own.
My family was involved in a multi-car wreck in the late 60s. We survived, with some injuries, but not everyone did, and that experience lead to the discovery that, had my Dad died, his pistols (he had half a dozen, which was more than anyone else in our circles) would have had to have been surrendered to the State. (NO COMPENSATION). IF surrendered to the State Police, they would be kept 30 days, then destroyed.
If surrendered to the County Sheriff, AND a permit was applied for, they would be held until the permit application was either approved or denied.
Mom immediately applied, and her permit had all Dads pistols on it. Both my brother and I applied when we came of age. Again with all Dad's (and Mom's) pistols on them.
I got my permit in 1975. 5 sets of fingerprints, 4 photographs, and 3 "character references" were required. Now, to illustrate the fact that these people (while not always current) NEVER FORGET, I moved to the west coast in 1979. In 2001 I got a letter from NYS, informing me that, since I was no longer a NY resident, my permit was no longer valid, and THEY WANTED IT BACK!!!
That's right, the paper permit (not even cardstock, but paper, and non-laminated at that) that they had issued in 1975, they wanted it back. ALSO they wanted me to tell them the whereabouts of the pistols on it. My Dad's guns that I hadn't seen since 1990 when we buried my Mother, NYS wanted me to tell them where they were....
Probably hoping to seize them, as my permit was no longer valid...
In 2003 my Dad passed and I flew back to NY to deal with that. I was able to have 3 of his pistols shipped to my FFL in WA because my brother still had them listed on his pistol permit so the NY FFL would do it.
SO yes there is another kind of "registration leading to confiscation" out there. If your state has a permit system, or a person registration system (FOID) do check carefully what happens to their firearms if they become deceased. Some places (like NY) will try to seize them as soon as they become aware of the owner's passing.
Other places treat them as just another part of the estate and see that they reach the inheritors. Delivery might be delayed by the state if the inheritor needs to obtain a permit/FOID or meet other legal requirements.