The 12.5 inch model may be sold by Beretta-USA only as a "Law Enforcement weapon", and all NFA rules apply to it, as its short barrel length restricts its civilian availability as a "Short Barreled Rifle" (any rifle with a barrel length less than 16 inches as described in the NFA Title 2), a category of firearms which is forbidden to own in certain States and that requires a BATFE Form 4 to be filed and a payment of $200.00.
This registration is a defense to prosecution if you possess the proper forms, processed in accordance with the National Firearms Act which includes a paid tax stamp and approval by the NFA branch of the BATFE.