Mass. Gen. Laws ch. 41 § 99A
Any member of the regular police or fire department and fire alarm division of a city or town appointed subsequent to August first, nineteen hundred and seventy-eight shall reside within fifteen miles of the limits of said city or town. Said distance shall be measured from the closest border limits of said city or town in which said member is employed to the closest border limits of the city or town in which said member lives; provided however, if any said city or town by local ordinance or by-law to which the provisions of paragraph (d) of section seven of chapter one hundred and fifty E of the General Laws shall apply, or by collective bargaining agreement shall require the members of a regular police or fire department appointed on or after August first, nineteen hundred and seventy-eight to be residents of such city or town, the provision of such local ordinance, by-law or collective bargaining agreement shall supersede the provision of this section and provided further such local ordinance, by-law or collective bargaining agreement shall apply only to those members of a regular police or fire department appointed subsequent to the adoption of such local ordinance, by-law or collective bargaining agreement.
Mass. Gen. Laws ch. 41, § 99A