Legality of carrying a flail?

In general, how legal is it in the United States to carry a flail around with you, preferably concealed? A flail is also known as a morning star or a mace; a fairly good picture of what I'm talking about is at http://en.wikipedia.org/wiki/Flail_%28weapon%29 -- how much trouble could I get in if I was carrying one of them, or is it perfectly fine, or are there just no statutes on the books?