Iowa Code § 595.3: License.

Previous to the solemnization of any marriage, a license for that purpose must be obtained from the county registrar. The license must not be granted in any case:

1. Where either party is under the age necessary to render the marriage valid.

2. Where either party is under eighteen years of age, unless the marriage is approved by a judge of the district court as provided by section 595.2.

3. Where either party is disqualified from making any civil contract.

4. Where the parties are within the degrees of consanguinity or affinity in which marriages are prohibited by law.

5. Where either party is a protected person under a guardianship and the court has made a finding that the protected person lacks the capacity to contract a valid marriage.