Iowa Code § 598.29: Annulling illegal marriage — causes.

Marriage may be annulled for the following causes:

1. Where the marriage between the parties is prohibited by law.

2. Where either party was impotent at the time of marriage.

3. Where either party had a husband or wife living at the time of the marriage, provided they have not, with a knowledge of such fact, lived and cohabited together after the death or marriage dissolution of the former spouse of such party.

4. Where either party was a protected person under a guardianship and was found by the court to lack the capacity to contract a valid marriage.