Actually, until 9/11, a pocket knife with a blade less than 4" was legal. But no serrated or partially serrated blades were allowed, because someone thought that they looked "menacing."

/rant on
It wasn't knives that caused 9/11, it was the attitude that "If we just do what they say, no one will get hurt." They acurately found the weak spot in security, and it was that aforementioned attitude. Now we should make sure the average person CAN carry a pocketknife.
/rant off

BTW, the word is spelled discreet. Another case of a spell checker not being able to pick the right homophone, perhaps? After watching my supervisor at work attempt to open a taped box with a steel ruler (!), I had just (gently) snapped open my RSK Griptilian and handed it to her when my new (to the company) manager walked up behind me. I think he visibly jumped, and said "Can you carry that at work?" I casually replied "Oh yeah, it's just a pocketknife," but I am being more discreet, and carrying an RSK Mini-Griptilian or my small Sebenza. Another excuse to add to my knife collection. <img src="/images/graemlins/smile.gif" alt="" /> Now I'm also carrying a little Gerber Ultralight LST (~2" blade) in the left watch pocket on my jeans for opening boxes, etc. I didn't like getting tape adhesive on my good knife anyway. It probably helps that our Facilities people all carry Leathermans and/or Gerber multitools, folding knives in belt sheaths, pagers, radios, cell phones, flashlights, etc. on their belts.