It’s somewhat a confusing mess right now, but one thing worth noting, TN removed SBRs and SBS from the state law this last July, so it will kind of be like CA and CO with Mary Jane, federally illegal but legal within the state. I have spoken with several state and my local LEO agencies about the matter, and they will supposedly not be assisting the feds with anything in this manner, though they warned that Metro and the other liberal citIes have and will continue despite the change in state law. Unlike CA and CO where the feds don’t care about drugs, I still think they will pounce on a gun owner with a soon to be illegal brace the first chance they get. There will possibly be an NFA amnesty where they waive the $200 fee to register your braced pistol, this would potentially include having to send a picture of it with the brace, so you couldn’t change it to a stock later. Many also suspect that this is just a way to get more AR’s added to their registry. Lots of information about it on YouTube.