Mont. Code Ann. § 19-18-612

Except for execution or withholding for the payment of child support or for the payment of spousal support for a spouse or former spouse who is the custodial parent of the child, payments made or to be made under this chapter are not subject to judgments, garnishment, execution, or other legal process. A person entitled to a pension may not assign the right, and the association and trustees may not recognize any assignment or pay over any sum assigned.