Mass. Gen. Laws ch. 149 § 178B
The state treasurer, the treasurer of any county, the treasurer of any state institution and the treasurer of any city or town having a by-law or ordinance or collective bargaining agreement so requiring shall, and unless contrary to a by-law or ordinance the treasurer of any other city or town or of any district may, deduct from each payment of salary to any employee of the commonwealth or of any such county, city, town or district such amount or amounts as such employee in a written authorization to such treasurer may specify for purchasing shares of, or making deposits in, or repaying any loan from any credit union operated by employees of the commonwealth or of any such county, city, town or district or by members of a state association of teachers or any savings or cooperative bank, trust company, or credit union incorporated in or chartered by the commonwealth; or any national banking association, federal savings and loan association or federal credit union located in the commonwealth; or any banking company or Morris Plan Company subject to chapter one hundred and seventy-two A, or any savings and loan association under the supervision of the commissioner of banks. Any such authorization may be withdrawn by the employee by giving at least thirty days notice in writing of such withdrawal to the state, county, municipal or district treasurer, or the treasurer of the state or county department or institution and by filing a copy with the treasurer of said credit union. Any treasurer making deductions under this section shall transmit the amounts so deducted to the treasurer of such credit union or to the appropriate officer of any other such bank or association for the purposes specified by the employee; provided, in the case of such a union, that he is satisfied by such evidence as he may require that the treasurer of the credit union has given bond as required by the law for the faithful performance of his duties. The treasurer of any city, town or district shall transmit the amounts so deducted to the credit union operated by members of a state association of teachers within fourteen days of the deduction. Moneys so deducted shall not be attached or taken upon execution or other process while in the custody of the treasurer making the deduction.
The state treasurer shall deduct from each payment of pension to any retiree of the commonwealth such amount or amounts as such retiree in a written authorization to the state treasurer may specify for purchasing shares of, or making deposits in, or repaying any loan from any credit union operated by employees of the commonwealth. Any such authorization may be withdrawn by the retiree by giving at least 30 days notice in writing of such withdrawal to the state treasurer and by filing a copy with the treasurer of said credit union. The state treasurer making deductions under this section shall transmit the amounts so deducted to the treasurer of such credit union for the purposes specified by the retiree; provided, however, that in the case of such a union, he is satisfied by such evidence as he may require that the treasurer of the credit union has given bond as required by the law for the faithful performance of his duties. Moneys so deducted shall not be attached or taken upon execution or other process while in the custody of the state treasurer, except when so authorized by any other provision of law.
Mass. Gen. Laws ch. 149, § 178B