Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 31, § 51

All positions in all cities shall be subject to the civil service law and rules except as provided by section forty-eight or other law and except that, in cities with less than one hundred thousand residents, positions which would fall within the labor service shall not be so subject unless the city council votes to accept the applicability of the civil service law and rules to the labor service.

Notwithstanding the provisions of section forty-eight, the following offices and positions in cities shall be subject to the civil service law and rules: (1) the position of parking meter supervisor in cities whose city councils vote to accept the applicability of civil service law and rules to such position; (2) the office or offices of chief of police or chief of fire department, or the officer performing similar duties, whatever his title, in cities which vote pursuant to the provisions of sections fifty-four and fifty-five to accept the applicability of the civil service law and rules to such office or offices; (3) any municipal office to which the civil service law and rules are made applicable pursuant to section fifty-three; and (4) any office or position to which the civil service law and rules were applicable immediately preceding the effective date of this chapter.