Mississippi Code Title 41. Public Health § 41-29-148

(1) It is not necessary for the state to negate any exemption in this article in any complaint, indictment or other pleading or in any trial, hearing, or other proceeding under said article. The burden of proof of any exemption or exception is upon the person claiming it.

(2) 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.