Sochin is correct, it's the ability to open the knife through centifical force or gravity that makes them illegal. Unfortunately, just about every knife with a heavy blade can be snapped open (I'm like that clerk, I can even make my Police snap open)therefore making all knives illegal. It's an odd law, the knife isn't illegal until it's opened illegally, yet in the right hands, all knives are illegal. But you can buy Spydercos, Emersons, BMs, and so on in knife stores across the country or buy them ove rthe internet. So obviously, the knife itself is no illegal. If you snap a knife open, you're asking for trouble. Personally, I don't know, nor have heard of any one being arrested for just carrying a Spyderco or similar knife. The law is rather vague, but because there hasn't been any real incidents no one here has tried to clarify the law. The fear is that if knife owners start to make a noise about clarity, all of these knives may be banned. Hence, no one wants to kick up a stink about it unless they really have to. So far, it hasn't been a problem, so we're stuck with ambiguity. The best advice I can give is don't worry about it, but don't be silly either-don't snap it open, and if you have to show it to police/security/etc. use both hands to open it.
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"Better to reign in Hell, than serve in Heav'n"
John Milton
There are only two types of people; those who understand this, and those who think they do.