(a) It shall not be necessary for the State to negate any exemption or exception set forth in this Article in any complaint, information, indictment, or other pleading or in any trial, hearing, or other proceeding under this Article, and the burden of proof of any such exemption or exception shall be upon the person claiming its benefit.
(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 shall be presumed not to be the holder of such registration or form, and the burden of proof shall be upon him to rebut such presumption.
(c) No liability shall be imposed by virtue of this Article upon any duly authorized officer, engaged in the lawful enforcement of this Article.