This is a good link to find out whether, when, or how carrying a sgian dubh (or any fixed-blade knife) is legal in your State. Remember, some States allow local governments to pass more restrictive laws, so it is always a good idea to research all of the pertinent laws before carrying a knife of any kind. This is a good place to start:

http://pweb.netcom.com/~brlevine/sta-law.htm