Yup, thanks to the good old NFA (National Firearms Act) that kind of weapon is classified as a Title II firearm (see National Firearms Act, ch. 757, 48 Stat. 1236 (1934)) and thanks to the 1986 FOPA (Firearms Owner's Protection Act...God I hate that title) it is illegal for any civilian to purchase any Title II weapon that was not registerd prior to May 19, 1986 (see 18 U.S.C. 922(o)).
So, you may see some folks with older vulcan type cannons, but nothing brand spanking new like that one in the hands of a civilian. Of course, you could probably get ahold of one, but I'm thinking the BATFE would show up and burn your house to the ground pretty quick.