I am a retired police officer and know the laws of Virginia and Alaska quite well. Never studied any other State's laws, but would bet you'll find a black powder as much a firearm as a smokeless firearm no matter where you are.
Police officers should know the laws they enforce. There may be some small localities that don't train their deputies or police officers so you should call your State Police, in your community, if you want to know the law. I wouldn't ask a judge. You might have to wait until he goes to his chamber to research law books. ;-) Besides... They don't want to be bothered by common people they have little respect for (sometimes, but not always the case).
Concealed weapon permits exist in Virginia, but not Alaska, where no citizen (exceptions are police officers, etc.) can legaly conceal a firearm. Although only a small portion of the weapon needs to be exposed, unless there has been recent rulings to the contrary. Concealed weapon laws vary from State to State, and in some States, even community to community, but if a concealed weapons law exist, you can be certain that black powder firearms carry the same designation as smokeless firearms. There may be different hunting seasons for muzzle loaders but I doubt seriously there are different laws of concealment.
As for a weapon of self defense... If it is all you have then go for it. Anything in hand is okay when it comes to protecting the life of you or some other victim. I can assure you I'd grab my 9mm, 357, or even my 38 before I'd grab my 1860 Colt or Walker 44. Not to say that my 12 guage would do better than any of them. Repairs to damaged walls or furnature would be my least concern in a life threatening situation. But... To each his own. If you feel good about black powder for self defense, then go for it. It's your life, or maybe your wife and children that is at stake.
Personally, I think every household should be trained and have safe but quick access to firearms for self defense. I can assure you that it would make a difference in the rate of home invasions. There would be less victims if the bad guys knew their intended victims were armed and ready. Bad guys have them in their house, in their cars, and on their person. The good guys should at least have them in their house, and even on their person if a permit is issued. I wouldn't want to have every citizen walking around with guns on their hips because I've seen the violent behavour of good law abiding citizens when anger clouds their judgement. Road rage or other temporary outburst of anger would make it unsafe to be in public. We need our firearm laws to keep people safe. We also need our firearms to keep people safe.
A felon responded to this post and I'm sure he or she knows that the felony firearm laws is a gross error in justice. I would agree that the laws should apply to those who use a firearm in the commission of a felony, or maybe if the felony was of a violent nature, but so many felons do not fit in those categories and don't deserve the same loss of rights. Ed.