From the Document: "On April 7, 2021, the White House announced that the Department of Justice has been directed to issue a proposed rule within 60 days (by June 6, 2021) to clarify when a device marketed as a stabilizing brace might turn a pistol into a short-barreled rifle. On December 18, 2020, the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) published guidance in the 'Federal Register' for public comment that indicated that it was preparing to reclassify certain 'heavier, larger handguns (pistols) equipped with stabilizing braces' as more stringently regulated 'short-barreled rifles.' Such a reclassification would retroactively trigger the more extensive paperwork and background check requirements of the 1934 National Firearms Act (NFA), and require registration of the owner and firearm with ATF. While this guidance was withdrawn on December 23, 2020, the proposed rule could address some of the same issues."
CRS In Focus, IF11763
Congressional Research Service: https://crsreports.congress.gov/