A "Bowie knife" for the purposes of that law would, I should think, be what is historically called a "Bowie knife", a large bladed knife with a single edge and a sharpened clip of one sort or another. Some clips are straight and some are curved. Since the law was written 150 or more years ago and never repealed, so it would apply, I should think, to what was then considered to be a "Bowie knife", but it is very seldom enforced today. I suspect that you'd have to be doing something pretty awkward to get busted for carrying a "Bowie knife" in Virginia, at least outside of the urban centers. I do know that for many years, I carried a Randall 6" Hunters' Bowie on my hip all around Fairfax and Loudoun Counties without unduly alarming anyone, including a number of police. But that was 35-40 years ago.
What we have is an antiquated law, a piece of history from the period of the pre-Civil War Era when a well handled knife was more than a match for the single shot muzzle-loading pistols of the day. With the appearance of Col. Colt's revolvers and the other revolvers that soon followed, the day of the Bowie as the supreme weapon passed into history and the laws became obsolete. But they were never repealed, and that is the problem. Do any of you know of a relatively recent prosecution under these 1840s laws? I would be very curious to see what a judge had ruled on that subject.
And I agree with Pendentive to the extent that a Kerambit would most likely land you in trouble wherever you are as there is no way that I can see to call it anything but a weapon and the police and prosecuting attornies will not take well to your carrying it.
But I do not agree with Pendentive's paranoia about Washington, DC, and knives. If you keep it within reason and don't go around "flourishing" it, you will probably have no problem with a folder having a blade of less than 3" except in some of the larger tourist attractions, such as the Capitol, Supreme Court, White House, Library of Congress, and the Smithsonian Museum complex. I am not completely certain of that last one, the Smithsonian Complex, but I would not want to hazard a knife there, as they are NOT part of the National Park Service, but a separate, quasi-governmental organization with its own rules and its own police powers. Some years ago, they weren't concerned, but I would not want to bet very much on that since 9/11.
As to being hassled by roving security people on the street, it is very unlikely unless you find yourself in a riot situation at, say, the International Monetary Fund or World Bank during their meetings when the crazies come to town. In that case, stand out of the way and try to be as agreeable with the police as you can. The DC police are very professional about these situations and if you are obviously not a part of them, they will generally let you alone if you do as you are told. Just remember that there are people out there who are actively provoking the police into taking violent action. I can remember walking past the White House in 1980 when I was caught between the pro-Khomeini and the anti-Khomeini Iranians who were about to go at each other with swords. A masked and helmeted DC policeman grabbed my arm and shoved me into a car, telling me to stay there. He didn't have to tell me twice, as it was the safest place around. When the fighting had moved on, he or another came over and let me go, with my profuse thanks.
...chances are, you'll never have to worry about it.