Any firearm with 2 or more "banned features" are considered "assault weapons". Unless an "assault weapon" was legally owned before to September 13, 1994 they are banned. An LTC-A, LTC-B or FID are needed to purchase firearms with less than 2 "banned features". Magazine restrictions must be followed for these firearms.
Some states have restrictions, banns, or require owners to register firearms they conceder to be "assault weapons". The definitions of an "assault weapon" varies widely from state to state. These definitions can include whether the gun is fully automatic, the magazine size it can carry, and others.