Marriages are voidable when:
one of the parties lacked capacity [see 767.313(1)(a)];
one of the parties was not yet of age [see 767.313(1)(c)]; -or-
the marriage was not legal in some other way [see 767.313(1)(d)].
COMMON LAW ANNULMENT
Historically marriages could be annulled when the parties had not consummated their relationship within a year. Wisconsin goes one step farther, and requires it to be an unknown physical limitation [see 767.313(1)(b)].
THE STATUE (767.313)(1) ANNULMENT
"Grounds; when suit may be brought. A court may annul a marriage upon any of the following grounds:
WI STAT 767.313(1)(a)
A party lacked capacity to consent to the marriage at the time the marriage was solemnized, either because of age, because of mental incapacity or infirmity or because of the influence of alcohol, drugs, or other incapacitating substances, or a party was induced to enter into a marriage by force or duress, or by fraud involving the essentials of marriage. Suit may be brought by either party, or by the legal representative of a party lacking the capacity to consent, no later than one year after the petitioner obtained knowledge of the described condition.
WI STAT 767.313(1)(b)
A party lacks the physical capacity to consummate the marriage by sexual intercourse, and at the time the marriage was solemnized the other party did not know of the incapacity. Suit may be brought by either party no later than one year after the petitioner obtained knowledge of the incapacity.
WI STAT 767.313(1)(c)
A party was 16 or 17 years of age and did not have the consent of his or her parent or guardian or judicial approval, or a party was under 16 years of age. Suit may be brought by the underaged party or a parent or guardian at any time prior to the party's attaining the age of 18 years, but a parent or guardian must bring suit within one year of obtaining knowledge of the marriage.
WI STAT 767.313(1)(d)
The marriage is prohibited by the laws of this state. Suit may be brought by either party within 10 years of the marriage, except that the 10-year limitation shall not apply where the marriage is prohibited because either party has another spouse living at the time of the marriage and the impediment has not been removed under s. 765.24.
WI STAT 767.313(2)
Judicial proceeding required; no annulment after death. A judicial proceeding is required to annul a marriage. A marriage may not be annulled after the death of a party to the marriage."