Iowa Code § 29A.52: Malice must be proved.

No action or proceeding shall be maintained against any officer appointing a military court or against any member of a military court or commission, officer or agent acting under its authority, or reviewing its proceedings, on account of the imposition of a fine or penalty or for the execution of a sentence of any person, unless it be shown that such officer, member or agent has acted from motives of malice.