Haw. Rev. Stat. § 580-26: Lack of mental capacity.

The marriage of a person who lacked the mental capacity to consent to the marriage may be annulled on the application of either party, or on the application of a guardian of the party who lacked capacity; provided that no sentence of nullity shall be pronounced if it appears that the parties freely cohabited as a married couple after the party who lacked mental capacity attained the mental capacity necessary to consent to marriage.