Mo. Rev. Stat. § 409.5-503: Evidentiary burden.

(a) In a civil action or administrative proceeding under this act, a person claiming an exemption, exception, preemption, or exclusion has the burden to prove the applicability of the claim.

(b) In a criminal proceeding under this act, a person claiming an exception or exclusion from definition has the burden of injecting the issue pursuant to section 556.051*, and a person claiming an exemption or qualification as a federal covered security has the burden of proving the claim as an affirmative defense pursuant to section 556.056*.