Banned because you can never illegalize weapons in the States. You've needed them ever since the British tried to stomp on you, ever since the Native Americans tried to stomp on you, and ever since the Mexicans tried to stomp on you, and there is every chance that all three groups will try to do that shit again.
Which is why you need as many scoped hand-cannons, anti-materiel rifles, and ammunition for every weapon since the 1700s crammed into your local Walmart.