I recall that in some state I lived in, it was legal to own a switchblade - but only if you were missing an arm! I saw one that I liked in a store in Atlanta - and the clerk said "you can't carry it, though". So I asked her, "so how do I get it out of the store"? The clerk just got totally confused. The girl I was with though that was pretty funny...
The laws on automatic knives are pretty strange.
As I understand it, here are some highlights.
1. Unless the state you live in specifically bans them, you can carry them IF they are made in that state.
2. You can carry one if you are a cop, or a member of the armed forces.
3. You can carry one if you are a firefighter, or an emergency services person.
4. Legally, you can own them in the majority of states, but as I read it, you cannot carry it from state to state, unless you fit in one of the top categories.
5. You can send it via UPS or FED EX, but not by U.S. Mail.
Confusing? Yep.