Could someone clarify the rules regarding folding or collapsible stocks?  I was browsing on an auction site and saw some semi Uzi's with folding stocks.  I thought that was illegal.  Does it have something to do with pre and post ban?  Thanks!

I can't tell you about the Uzi's.

If you own a postban rifle that meets the qualification as a "defined" semi-automatic "assault weapon" then it could have a folding or collapsible stock on it with nothering else.

Lets say that you owned a post ban Mini-14.
It meets that "qualifications" to be CONSIDERED to be a defined "assault weapon":

1.  Semi-automatic rifle
2.  Ability to accept hi-capacity magazines

The Mini-14 does.

Then you could have one of the following items and still NOT be a defined "assault weapon":

1.  Pistol grip
2.  Folding stock ONLY
3.  Collapsable stock ONLY
4.  Flash hider
5.  Ability to mount a grenade launcher
6.  Bayonet lug

Just use a posban AR15 as your example.

Semi-automatic rifle.
Ability to accept hi-capacity magazines.
Pistol grip.