I know that normally if you take personal property with you out of the United States then you do not have to pay duty on it when it comes back with you. For example, if you own a Swiss watch and return to the United States you do not have to either declare or pay duty on that watch because it is your personal property.
Does this apply to tobacco as well? For example, if I have a box of 200 cigars that I bring with me out of the country to smoke or share with friends and then I return to the United States with that box of cigars, do I need to declare it or pay duty on it? How do I prove they are my cigars? Is the U.S. purchase receipt sufficient?