In 1989, Bush Sr. signed a bill that modified the import rules for guns that were established by GCA68. This is usually referred to as the "89 Import Ban". Basically, it was the first attempt to ban the import of "military-style semi-autos" based on "military features."
Under the new rules, beginning in 1990, any imported semi-auto that accepted detachable mags could not have any of the following "military features":
- pistol grip
- folding/collapsable stock
- bayonet lug
- flash suppressor/threaded barrel
- military bipod
The Chinese response to this was the MAK-90, or "Modified AK, 1990." It was an AK with no bayo lug or threaded barrel, and a fixed "thumbhole" stock. BATF had ruled that, for the purposes of the new '89 Import rules, a thumbhole was NOT a military feature, and therefore it was okay. Uzi, FAL, and G3 clones (and probably many others) continued to be imported with these awful thumbhole stocks.
Then came the 1994 AW ban, which, besides banning some guns by name, banned other guns by features. Plus, this law affected BOTH imports and domestics. Under the wording of THIS law, BATF decided that a thumbhole stock "enclosed" a pistol grip, and therefore still counted as an evil item.
Given that ARs are (almost always) domestic, the 89 Import Ban don't apply at all; just the 1994 rules. But, that means that a thumbhole is still a pistol grip, and so you don't get to "trade" evil items.
-Troy