Mo. Rev. Stat. § 86.563
No portion of said pension fund shall before or after its order of distribution by the board of trustees to the person entitled thereto, be held, seized, taken, subjected to or detained or levied on by virtue of any attachment, execution, injunction, writ, interlocutory or other order or decree or any process or proceedings whatever issued out of or by any court for the payment or satisfaction in whole or in part of any debt, damage, claim, demand or judgment against the beneficiary of this fund and no assignment by said beneficiary shall be valid, but the same shall be null and void, and said fund shall be held and distributed for the purpose of sections 86.510 to 86.577 solely to the persons entitled thereto and for no other purpose whatever.
Effective dates prior to 1940 may not be the actual effective date. See FAQ 'When do laws become effective?'
§ 86.563, RSMo
RSMo 1939 § 9491