When I first saw those braces, I wondered about them.When I saw people using them as stocks, I knew it was a matter of time.
If you want braces, don't use them as stocks. Tony Shaffer put out pics of him using one as a stock. The NRA put out ad with woman in wheelchair doing so. When something like that gets flaunted like that, ATF'nE had to at least look into it.
Some may see SBR law as unconstitutional. But it's the law.
See also: https://parler.com/comment/459f1e03bcbe474791360b5c85303fb6
SBR: "Short-Barreled Rifle," which are restricted by 1934 National Firearms Act (NFA).