Mo. Rev. Stat. § 456.1-107: Governing law.

The meaning and effect of the terms of a trust are determined by:

(1) the law of the jurisdiction designated in the terms unless the designation of that jurisdiction's law is contrary to a strong public policy of the jurisdiction having the most significant relationship to the matter at issue; or

(2) in the absence of a controlling designation in the terms of the trust, the law of the jurisdiction having the most significant relationship to the matter at issue.