text: when do marriage and divorce become unlawful? you can give references if you want. i don't know about divorce,but marriage is unlawful in a few situations. for instance: if you are already married. if you are marrying a family member. if you are homosexual in some states. if you are being married by someone who is not authorized by the state to legally perform a marriage. if you do not have the proper license in some states. if you are attempting to marry someone who is not of legal age. if you are attempting to marry someone who is not legally able to enter into a legal contract because of their mental status. i'm sure there are quite a few more,but i'm tired. fire me...