961.56 Burden of proof; liabilities.
(1) It is not necessary for the state to negate any exemption or exception in this chapter in any complaint, information, indictment or other pleading or in any trial, hearing or other proceeding under this chapter. 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 federal registration or order form, the person is presumed not to be the holder of the registration or form. The burden of proof is upon the person to rebut the presumption.

(3) No liability is imposed by this chapter upon any authorized state, county or municipal officer or employee engaged in the lawful performance of the officer’s or employee’s duties.