Mass. Gen. Laws ch. 171 § 36
Any designation of any beneficiary in connection with and as provided by an instrument intended to establish a pension, profit-sharing or other deferred compensation or retirement plan, trust or custodial account described in one or more of the following sections of the Internal Revenue Code of the United States, and in effect from time to time, shall be effective according to its terms, notwithstanding any purported testamentary disposition allowed by statute, by operation of law or otherwise to the contrary; section four hundred and one (a), section four hundred and one (f), section four hundred and three (b)(7), section four hundred and five (a), section four hundred and eight (a), and section four hundred and eight (h). Nothing in this section is intended to limit, by implication or otherwise, any nonstatutory right of an employee to designate one or more beneficiaries in the employees' interest under any retirement plan not described in this section or under any other employee benefit plan.
Mass. Gen. Laws ch. 171, § 36