Marriages void ab initio–In general.
The following marriages are prohibited in the District of Columbia and shall be absolutely void ab initio, without being so decreed, and their nullity may be shown in any collateral proceedings, namely:
(1) The marriage of a man with his grandmother, grandfather’s wife, wife’s grandmother, father’s sister, mother’s sister, mother, stepmother, wife’s mother, daughter, wife’s daughter, son’s wife, sister, son’s daughter, daughter’s daughter, son’s son’s wife, daughter’s son’s wife, wife’s son’s daughter, wife’s daughter’s daughter, brother’s daughter, sister’s daughter;
(2) The marriage of a woman with her grandfather, grandmother’s husband, husband’s grandfather, father’s brother, mother’s brother, father, stepfather, husband’s father, son, husband’s son, daughter’s husband, brother, son’s son, daughter’s son, son’s daughter’s husband, daughter’s daughter’s husband, husband’s son’s son, husband’s daughter’s son, brother’s son, sister’s son;
(3) The marriage of any persons either of whom has been previously married and whose previous marriage has not been terminated by death or a decree of divorce.
(D.C. Statutes section 46-401)
Dean v. District of Columbia, 653 A.2d 307 (D.C. 1995)
This decision by the District of Columbia’s highest court ruled that there is no fundamental right to same-sex marriage.