If you are a nonresident you must present a valid passport with a valid visa. If you are on a student visa, you must show a valid I-20 form showing enrollment in your college or university. Failure to do so may cause reentry into the United States to be denied. Duty free items you may bring back include on hundred cigars and two hundred cigarettes, if not made in Cuba. You may bring back $400 worth of goods not on the prohibited list.