OK, DC has a 3" blade limit which is enforced wherever there is a metal detector, such as at the Holocaust Museum or at the Archives, I have been checked at both and 3" is OK, or was. I have never been asked about my pocket clip on the street or in the subway. The technical limit in federal offices is 2.5", but some say no blades at all! If you go to visit anyone in a federal office, best leave your knives in the car or your motel room. The same applies, in spades, for the White House, the U.S. Capitol, and the Supreme Court. The White House should be self-explanatory, while the U.S. Capitol Police have had an experience of a nutcase openning up on a line of tourists a couple of years ago and killing two police before they stopped him. They are very paranoid, what with that and bombs going off over there on an average of one every two or three years, so don't even think of trying to push them. As for the Supreme Court, well, they run their own little feifdom over there and you just have to do as you're told or not go there.
Virginia, as a commonwealth, has no real restrictions, other htan the usual ones on switchblades and gravity knives, but the local jusrisdictions are different. I would not carry anything over 4" in Arlington, Fairfax, or any of the cities around DC, such as Alexandria. And I would not be real obvious about it in them. Richmond, according to Professor, has a very rigid 3" limit, so beware. Other than that, I would not be too concerned about Virginia if you are out in the country, it is generally a pretty cool place where carrying sharp, pointy things is concerned. It also has "shall issue" CCW permits, much to the horror of the Washington Post.
