"As to the pistol brace ruling, I’m curious how that affected all of those ‘free’ ‘provisional’ SBR Form 1’s. Are they now null and void and all of those registered guns now have to have the stocks removed because they are back to pistol status?"

That precise question has been raised elsewhere, and several lawsharks, much more conversant in NFA law than I, say that all the free F1s are and will remain valid. Some previous case law controlling.

The registrations weren't 'provisional'. When approved, it was 'pursuant' to the rule that provided for the tax free registration.

What's really interesting about this, for the time being and until we see whether the bureaucraps at ATF decide to appeal, what's now possible, according to case law going back to 1992, is that a person can replace the stock with a brace and the gun reverts to being a handgun.
That eliminates the requirement to get an approved 5320.20 form for interstate travel, which I figure just chaps some ATF agent's hide.

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