Mo. Rev. Stat. § 169.090: Funds not subject to execution, garnishment, attachment.

Neither the funds belonging to the retirement system nor any benefit accrued or accruing to any person under the provisions of sections 169.010 to 169.130 shall be subject to execution, garnishment, attachment or any other process whatsoever, nor shall they be assignable, except in a proceeding instituted for spousal maintenance or child support and as in sections 169.010 to 169.130 specifically provided.