In the jurisdiction where I practice (Utah), the law is:
76-7-103. Adultery.
(1) A married person commits adultery when he voluntarily has sexual intercourse with a person other than his spouse.
(2) Adultery is a class B misdemeanor.
There are few states, however, where adultery is a felony. And here is all you need to verify:
Idaho Statutes, Title 18, Crimes and Punishments, Chapter 66, Title 18, Section 6601
18-6601. ADULTERY. A married man who has sexual intercourse with a woman not his wife, an unmarried man who has sexual intercourse with a married woman, a married woman who has sexual intercourse with a man not her husband, and an unmarried woman who has sexual intercourse with a married man, shall be guilty of adultery, and shall be punished by a fine of not less than $100, or by imprisonment in the county jail for not less than three months, or by imprisonment in the state penitentiary for a period not exceeding three years, or in the county jail for a period not exceeding one year, or by fine not exceeding $1000.
Massachusetts general laws Title I, Chapter 272, Section 14:
A married person who has sexual intercourse with a person not his spouse or an unmarried person who has sexual intercourse with a married person shall be guilty of adultery and shall be punished by imprisonment in the state prison for not more than three years or in jail for not more than two years or by a fine of not more than five hundred dollars.
Because adultery is a crime can lead to a prison sentence of up to three years it is a felony.
Oklahoma Statutes, Title 21. Crimes and Punishments §21-871. Adultery defined – Who may institute prosecution.
Adultery is the unlawful voluntary sexual intercourse of a married person with one of the opposite sex; and when the crime is between persons, only one of whom is married, both are guilty of adultery. Prosecution for adultery can be commenced and carried on against either of the parties to the crime only by his or her own husband or wife as the case may be, or by the husband or wife of the other party to the crime: Provided, that any person may make complaint when persons are living together in open and notorious adultery.
Oklahoma law provides that adultery offenders face felony charges, punishable by imprisonment in the state penitentiary for up to five years or a fine up to $500 or both:
Oklahoma Statutes, Title 21. Crimes and Punishments §21-872. Punishment for adultery.
Any person guilty of the crime of adultery shall be guilty of a felony and punished by imprisonment in the State Penitentiary not exceeding five (5) years or by a fine not exceeding Five Hundred Dollars ($500.00), or by both such fine and imprisonment.
Oklahoma Statutes :: Title 43. Marriage and Family :: §43-123. Remarriage and cohabitation – Appeal from judgment.:
It is also unlawful for a divorced party to remarry again in Oklahoma within six months of the decree of divorce.
Unlawful to Marry Within 6 Months from Date of Divorce Decree:
Oklahoma Statutes, Title 43. Marriage, Divorce and Alimony, Section 123 – Unlawful to Marry Within 6 Months from Date of Divorce Decree – Penalty for Remarriage and Cohabitation-Appeal
It shall be unlawful for either party to an action for divorce whose former husband or wife is living to marry in this state a person other than the divorced spouse within six (6) months from date of decree of divorce granted in this state, or to cohabit with such other person in this state during said period if the marriage took place in another state; and if an appeal be commenced from said decree, it shall be unlawful for either party to such cause to marry any other person and cohabit with such person in this state until the expiration of thirty (30) days from the date on which final judgment shall be rendered pursuant to such appeal. Any person violating the provisions of this section by such marriage shall be deemed guilty of the felony of bigamy. Any person violating the provisions of this section by such cohabitation shall be deemed guilty of the felony of adultery.
An appeal from a judgment granting or denying a divorce shall be made in the same manner as in any other civil case.
Michigan Penal Code, Act 328 of 1931, 750.30 Adultery; punishment. Sec. 30.
Punishment—Any person who shall commit adultery shall be guilty of a felony; and when the crime is committed between a married woman and a man who is unmarried, the man shall be guilty of adultery, and liable to the same punishment.
Wisconsin Statutes
944.16 Adultery. Whoever does either of the following is guilty of a Class I felony:
(1) A married person who has sexual intercourse with a person not the married person’s spouse; or
(2) A person who has sexual intercourse with a person who is married to another.
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