Please show me any statute, federal or state, that prohibits anyone from sex based on whether or not they are married.
Here is a few states that issue marriage license.
Alabama Alaska Arizona Arkansas
California Colorado Connecticut Delaware
Florida Georgia Hawaii Idaho
Illinois Indiana Iowa Kansas
Kentucky Louisiana Maine Maryland
Massachusetts Michigan Minnesota Mississippi
Missouri Montana Nebraska Nevada
New Hampshire New Jersey New Mexico New York
North Carolina North Dakota Ohio Oklahoma
Oregon Pennsylvania Rhode Island South Carolina
South Dakota Tennessee Texas Utah
Vermont Virginia Washington West Virginia
Wisconsin Wyoming
Here is a list of the states that do not enforce the law:
Alabama Alaska Arizona Arkansas
California Colorado Connecticut Delaware
Florida Georgia Hawaii Idaho
Illinois Indiana Iowa Kansas
Kentucky Louisiana Maine Maryland
Massachusetts Michigan Minnesota Mississippi
Missouri Montana Nebraska Nevada
New Hampshire New Jersey New Mexico New York
North Carolina North Dakota Ohio Oklahoma
Oregon Pennsylvania Rhode Island South Carolina
South Dakota Tennessee Texas Utah
Vermont Virginia Washington West Virginia
Wisconsin Wyoming