In most states first cousins cannot marry. However, in some states it is allowed. For example, Tennessee law does not forbid first cousins to marry. In Ohio the parties must be no nearer than second cousins. Arizona law provides that first cousins cannot requirement for a blood test for rubella immunity. Informed consent must be recorded on a form provided by the department and must be signed by both applicants. The informed consent form must include:
(a) the reasons for undergoing a blood test for rubella immunity;
(b) the information that the results would provide about the woman’s rubella antibody status;
(c) the risks associated with remaining uninformed of the rubella antibody status, including the potential risks posed to a fetus, particularly in the first trimester of pregnancy; and
(d) contact information indicating where applicants may obtain additional information regarding rubella and rubella immunity testing.
(3) A person who by law is able to obtain a marriage license in this state is also able to give consent to any examinations, tests, or waivers required or allowed by this section. In submitting the blood specimen to the laboratory, the physician or other person authorized to issue a medical certificate shall designate that it is a premarital test.
Many states have rules that require testing of pregnant women for HIV, but that such requirements apply to pregnant women, not simply those who are married.
Courts will generally allow parties who are first cousins to remain married even if they reside in a state that does not allow such marriages. For example, in Mason v. Mason (2002), an Indiana appeals court refused to grant a man who had legally married his first cousin in Tennessee a divorce in Indiana. The court wrote that as a matter of comity (legal reciprocity), Indiana can choose to recognize Tennessee marriages between first cousins, even though such a marriage could not be validly contracted between residents of Indiana.