Laws prohibiting cohabitation and sexual relations outside marriage were very common until about the1970s. Though most of these laws have been repealed or are no longer enforced, they still exist in some state statutes. Eight states still have laws prohibiting cohabitation, which is usually defined as two individuals living together as husband and wife without being legally married. Nine states prohibit fornication, which is usually defined as consensual sexual intercourse outside marriage. More than 15 states prohibit sodomy, which includes any “unnatural” sexual activity, such as anal or oral sex. Several of these statutes apply specifically to homosexual activity.

While most of these criminal laws are clearly antiquated, they are sometimes enforced. In the United States Supreme Court case of Bowers v. Hardwick in 1986, the court upheld the enforcement of a criminal statute prohibiting sodomy between two homosexual men. Criminal statutes proscribing private sexual activity do not violate the federal constitution under Bowers, though some state courts have held that similar statutes are unconstitutional under the relevant state constitutions.