Mass. Gen. Laws ch. 180 § 17J
Deductions on payroll schedules may be made from the salary of any state, county, municipal or other public employee of an amount which such employee may specify in writing to any state, county or municipal officer, or public department head, board, commission or agency by whom or which he is employed, for any insurance or employee benefit offered in conjunction with the employee organization, which, in accordance with the provisions of chapter one hundred and fifty E is duly recognized by the employer or designated by the labor relations commission as the exclusive bargaining agent for the appropriate unit in which such employee is employed; provided, however, that such purpose has been approved by the comptroller. Any such authorization may be withdrawn by the employee by giving at least sixty days notice in writing to the state, county or municipal officer, or public department head, board, commission or agency by whom or which he is then employed.
The state treasurer, the common paymaster, as defined in section one hundred and thirty-three of chapter one hundred and seventy-five, or the treasurer of the county or municipality by which such employee is employed, shall deduct from the salary of such employee such amount of authorized deductions as may be certified to him on the payroll and transmit the sum so deducted to the recipient specified by such employee.
Mass. Gen. Laws ch. 180, § 17J