Mo. Rev. Stat. § 379.125

Any company or association, other than life, organized under the provisions of chapter 379 may cause itself to be wholly or partially reinsured against any loss arising from any risk which it may have undertaken, and in like manner may reinsure or guarantee any other corporation doing the same kind of business as itself (including, for policies issued outside of the United States, insurance of life risks that are attached as riders to policies, provided that the aggregate premium assumed on an annual basis pursuant to such life risks does not exceed three percent of the capital and surplus of such company as of the thirty-first day of December of the preceding year), against loss arising from any risks that shall have been or may be undertaken by such corporation, or may join with any such corporation in any such risk, and may make and enter into all manner of contracts relating to such reinsurance and joint insurance, and the terms upon which the same shall be conducted; provided, however, any company reinsuring the whole of any single risk or risks the same being a substantial portion of all risks insured by the company shall be subject to the provisions of section 375.241 *.