As the Supreme Court considers the constitutionality of laws banning same-sex marriage later this month, few have noticed that the case can easily be resolved under existing precedent.
Laws banning gay marriage are unconstitutional because they discriminate on the basis of gender. If same-sex marriage is forbidden, Anne is allowed to marry Bob, but Charles can't. Charles is denied the right to marry Bob, solely because Charles is a man. Denial of a legal right solely because of gender is the very essence of sex discrimination.