My standard comment about the best way to ban or regulate "assault rifles" was to consider them machineguns citing the Federal Definition of a machinegun (26 USC 5845(b)):
any weapon which shoots, is designed to shoot, or can be readily restored to shoot, automatically more than one shot, without manual reloading, by a single function of the trigger. The term shall also include the frame or receiver of any such weapon, any part designed and intended solely and exclusively, or combination of parts designed and intended, for use in converting a weapon into a machinegun, and any combination of parts from which a machinegun can be assembled if such parts are in the possession or under the control of a person.
The designed to shoot, or can be readily restored to shoot language makes pretty much every semi-automatic firearm on the market a machinegun! This is because "designed to shoot" can include weapons such as the British L1A1-SLR, which was never made with fully automatic capability, but because it is an FN-FAL varient (whichwas designed to fire in full-auto mode) is considered a machinegun by BATF! Likewise, this would include things such as the H&K 94, the semiauto civvy version of the MP5.
DC's law uses the fact that a firearm can use a magazine with a capacity of over 11 shots to make it a prohibited weapon.
The other fun bit is the "can be readily restored to shoot" language. U.S. v. Oakes, 564 F.2d 384 (10th Cir 1977) is a case where a machinegun with a welded barrel was considered "readily restorable to shoot". There is another case out there where "readily restorable to shoot" was taken to mean required 48 hours of labour with a special tool! I can't find the case, but I am sure someone with a law library and time could do that research.
Likewise, you can find full auto-conversion manuals out there for various semi-auto firearms. While you would be a fool to want a full auto-version and I am not sure I would recomend these conversions, the manuals do exist. Such manuals are proof that these weapons are "readily restorable to shoot".
I forgot to add that it is impossible to deactivate firearms (render inoperable) under federal law because of the arcane definition of readily restorable. The US requires that 1/4" cuts are made in the receiver: making them useless to the collector. British law is getting tighter on this since the Jill Dando slaying.
So, taking my question at the beginning: President George HW Bush created the "Assault Weapons Importation Ban" with an executive order in March 1989 as a reaction to the Cleveland Elementary School mass shooting in Stockton, California, United States.
Future post in this series: why are US gun laws becoming laxer?