After nosing around a bit, I think that thread on "awbansunset.com" comes to the correct conclusion: there was most likely no actual E.O. from GHWB in 1989. Instead, the BATF began scrutinizing firearms for certain characteristics before approving import licenses, etc. That agency is evidently so authorized under the Gun Control Act of 1968.
Of course, BATF most likely did that at the President's request - keep in mind that similar actions were taken against the importing of the "Streetsweeper" shotgun during Reagan's second term. BATF's authority to makes these sort of calls does not, unfortunately, sunset. If I understand the situation correctly, even if the Assault weapons ban does evaporate in 2004, BATF can simply fall back on its old protocol and continue to screw with us. Have a look:
Semi-Auto FAQs
There's way too many weirdo gun laws out there. For instance, the Glock 25..
The BATF needs to simply be dismantled. There's no benefit for it.
I'm not for full access to any weapon anyone wants. There should be local limits on so called 'class-3' stuff like full auto and suppressors. However, banning calibers and certain stocks and mags over 10 rounds is plain unconstitutional.
I think the current court stuff going on in CA will go to the supreme court finally. This subject needs to be like the 1st amemndment, simple. They can make certain limits, but not many.
I hope the USSC will finally come down and affirm what the 2nd plainly says. That's their job anyway.