Section 124.507 - Burden of proof - liabilities1. It is not necessary for the state to negate any exemption or exception set forth in this chapter in any complaint, information, indictment or other pleading or in any trial, hearing, or other proceeding under this chapter. The proof of entitlement to any exemption or exception by the person claiming its benefit shall be a valid defense.2. The absence of proof that a person is the duly authorized holder of an appropriate registration or order form issued under this chapter creates a rebuttable presumption that the person is not the holder of such registration or form.3. No liability shall be imposed by virtue of this chapter upon any authorized state, county or municipal officer, engaged in the lawful performance of the officer's duties.C24, 27, 31, 35, §3156; C39, §3169.18; C46, 50, 54, 58, 62, §204.19; C66, 71, §204.18; C73, 75, 77, 79, 81, §204.507 C93, §124.507