Mass. Gen. Laws ch. 32 § 19
The funds of each system established under the provisions of sections one to twenty-eight, inclusive, so far as they are invested in personal property, shall be exempt from taxation. The rights of a member to an annuity, pension or retirement allowance, such annuity, pension or retirement allowance itself, and all his rights in the funds of any system established under the provisions of such sections, shall be exempt from taxation, including income taxes levied under the provisions of chapter sixty-two, and from the operation of any law relating to bankruptcy or insolvency and shall not be attached or taken upon execution or other process. That portion of the estate of any deceased member consisting of any sum or sums received from any system under the provisions of sections one to twenty-eight, inclusive, shall not be included in computing any legacy or succession tax under the provisions of chapter sixty-five. No assignment of any right in or to any funds, annuities, pensions or retirement allowances under any system shall be valid except such assignment as may be made for the purpose of making restitution in the case of dereliction of duty by any member as set forth in section fifteen, and except such assignment made in writing by a retired member, authorizing the board to withhold each month such amount as he may designate for the payment of subscriber premiums applicable to a hospitalization, medical and surgical insurance, or to a life insurance, in effect with a nonprofit hospital and medical service corporation or insurance company at the time of his retirement, and except such assignment made in writing by a retired member authorizing the board to withhold each month such amount as he may designate for the payment of income taxes levied under the Internal Revenue Code of the United States or the General Laws of the commonwealth. No assignment shall be permitted in the case of a retired member of the teachers' retirement system for the payment of the monthly premium for an insurance policy issued under chapter thirty-two B, except as provided for in section nineteen B of this chapter or in section twelve of chapter thirty-two A. For persons making the election provided for in subdivision (1) of section nineteen B, such premium payments shall be paid by the retired member to the treasurer of the governmental unit to which the group policy under which the member is insured was issued, in accordance with such requirements as such treasurer may prescribe.
Nothing in this section shall prevent a member's annuity pension, retirement allowance or return of accumulated total deductions 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, two hundred and nine A, two hundred and nine C, two hundred and seventy-three, or received, entered or registered pursuant to chapter 209D, or an assignment of marital property under chapter two hundred and eight.
Mass. Gen. Laws ch. 32, § 19