Iowa Code § 189.16: Possession and control of adulterated and improperly labeled articles.

1. Except as provided in subsection 2, a person in possession or having control of an article which is adulterated or which is improperly labeled according to the provisions of this subtitle shall be presumed to know that the article is adulterated or improperly labeled. A person’s possession of an adulterated or improperly labeled article shall be prima facie evidence that the person intends to violate the provisions of this subtitle.

2. This section does not apply to the possession or control of any of the following:

a. Grain by a person regulated under chapter 203, 203C, or 203D.

b. Mining materials including coal by a person regulated under chapter 207 or 208.

c. A controlled substance as provided in chapter 124.