Iowa Code § 504.304: Ultra vires.

1. Except as provided in subsection 2, the validity of corporate action shall not be challenged on the ground that the corporation lacks or lacked power to act.

2. A corporation’s power to act may be challenged in a proceeding against the corporation to enjoin an act when a third party has not acquired rights. The proceeding may be brought by the attorney general, a director, or by a member or members in a derivative proceeding.

3. A corporation’s power to act may be challenged in a proceeding against an incumbent or former director, officer, employee, or agent of the corporation. The proceeding may be brought by a director, the corporation, directly, derivatively, or through a receiver, a trustee or other legal representative, or in the case of a public benefit corporation, by the attorney general.