I posted this in the legislation thread, but if some of you have not seen it, here is Thomas Massie educating the head of the AFT on the absurdity of this move. At the 1:10 mark, Massie corners Dettelbach on the original SB Brace and it's separation from the buffer tube.
Well stated Mr. Massie...the ATF does not have the legal authority to do what they did!