Iowa Code § 403A.17

All property, including funds, owned or held by a municipality for the purposes of this chapter shall be exempt from levy and sale by virtue of an execution, and no execution or other judicial process shall issue against the same nor shall any judgment against the municipality be a charge or lien upon such property. However, the provisions of this section shall not apply to or limit the right of obligees to foreclose or otherwise enforce any mortgage or other security executed or issued pursuant to this chapter or the right of obligees to pursue any remedies for the enforcement of any pledge or lien on rents, fees, or revenues or the right of the federal government to pursue any remedies conferred upon it pursuant to the provisions of this chapter.