Mass. Gen. Laws ch. 170 § 23
The property of the retirement association, the portion of the wages or salary of any employee deducted or to be deducted under sections 21 and 22, the right of an employee to an annuity or pension, and all of the employee's rights in the funds of the retirement association, shall be exempt from taxation and from the operation of any law relating to insolvency, and shall not be attached or taken on execution or other process to satisfy any debt or liability of the retirement association, a participating bank or any employee member of the retirement association. No assignment of any right in or to said funds or of any pension or annuity payable under section 21 shall be valid, except that deferred annuity contracts purchased by a participating bank on account of past service of eligible employees may be assigned to such bank prior to actual retirement.
Nothing in this section shall prevent an employee's annuity or pension from being attached, taken on execution, assigned, or subject to other process to satisfy a support order under chapter 208, 209 or 273.
Mass. Gen. Laws ch. 170, § 23