ANSWER:
The law in West Virginia concerning adultery is set forth in West Virginia Code § 61-8-3. Text of the statute is as folllows:
If any person commit adultery or fornication, he shall be guilty of a misdemeanor, and, upon conviction, shall be fined not less than twenty dollars.

Also be aware of WV Code § 61-8-4. Lewd and lascivious cohabitation and conduct; penalty; when persons presumed to be unmarried.
That statute reads as follows:
If any persons, not married to each other, lewdly and lasciviously associate and cohabit together, or, whether married or not, be guilty of open or gross lewdness and lasciviousness, they shall be guilty of a misdemeanor, and, upon conviction, shall be fined not less than fifty dollars, and may, in the discretion of the court, be imprisoned not exceeding six months, and, upon a repetition of the offense, they shall, upon conviction, be confined in jail not less than six nor more than twelve months. In prosecutions for adultery and fornication, and for lewdly and lasciviously cohabiting together, the persons named in the indictment shall be presumed to be unmarried persons in the absence of proof to the contrary.

Best advice is to ignore the Nike rule and Just DON'T Do It.

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