Mass. Gen. Laws ch. 32 § 41
The property of every such association, the right of an employee to an annuity, pension or endowment, and all his rights in the funds of the association, shall be exempt from taxation and from the operation of any law relating to bankruptcy or insolvency, and shall not be attached or taken on execution or other process to satisfy any debt or liability of the employer or of any member of the association.
No assignment of any right in or to said funds or of any pension, annuity or endowment payable under section thirty-nine or forty shall be valid.
Nothing in this section shall prevent an employee's annuity, pension, or endowment from being attached, taken on execution, assigned, or subject to other process to satisfy a support order under chapter two hundred and eight, two hundred and nine, or two hundred and seventy-three.
Mass. Gen. Laws ch. 32, § 41