Iowa Code § 659.5: Defamatory statement by radio.

The owner, lessee, licensee, or operator of a radio broadcasting station, and the agents or employees of any such owner, lessee, licensee, or operator, shall not be liable for any damages for any defamatory statement published or uttered in or as a part of a radio broadcast, by one other than such owner, lessee, licensee, or operator, or agent or employee thereof, if such owner, lessee, licensee, operator, agent, or employee shall prove the exercise of due care to prevent the publication or utterance of such statement in such broadcasts.