Marriages void from date of decree; age of consent.

The following marriages in said District shall be illegal, and shall be void from the time when their nullity shall be declared by decree, namely: (1) The marriage of a person adjudged to be, or to have been at the time a marriage was performed, unable by reason of mental incapacity to give valid consent to marriage; (2) Any marriage the consent to which of either party has been procured by force or fraud; (3) Repealed. (4) When either of the parties is under the age of consent, which is hereby declared to be 18 years of age.