(a) It is not necessary for the state to negate any exemption or exception in this article in any complaint, accusation, indictment, or other pleading or in any trial, hearing, or other proceeding under this article. The burden of proof of any exemption or exception is upon the person claiming it.
(b) In the absence of proof that a person is the duly authorized holder of an appropriate registration or order form issued under this article, he is presumed not to be the holder of the registration or form. The burden of proof is upon him to rebut the presumption.
(c) No liability is imposed by this article upon any authorized state,
county, or municipal officer engaged in the lawful performance of his
duties.