Mass. Gen. Laws ch. 150E § 3
The commission shall prescribe rules and regulations and establish procedures for the determination of appropriate bargaining units which shall be consistent with the purposes of providing for stable and continuing labor relations, giving due regard to such criteria as community of interest, efficiency of operations and effective dealings, and to safeguarding the rights of employees to effective representation. No unit shall include both professional and nonprofessional employees unless a majority of such professional employees votes for inclusion in such unit; provided, however, that in any fire department, or any department in whole or in part engaging in, or having the responsibility of, fire fighting, no uniformed member of the department subordinate to a fire commission, fire commissioner, public safety director, board of engineers or chief of department shall be classified as a professional, confidential, executive, administrative or other managerial employee for the purpose of this chapter.
No elected or appointed official, member of any board or commission, representative of a public employer, including the administrative officer, director or chief of a department or agency of the commonwealth or any political subdivision thereof, or clerk, temporary clerk or assistant clerk of any court, or chief probation officer or acting chief probation officer of any court or region, including, without limitation within the term, any division or department of the trial court, or any other managerial or confidential employee shall be included in an appropriate bargaining unit or entitled to coverage under this chapter.
The appropriate bargaining unit in the case of the uniformed members of the state police shall be all such uniformed members in titles below the rank of lieutenant. The appropriate bargaining units for judicial employees within the provisions of this chapter shall be a public safety professional unit composed of all probation officers and court officers, and a unit composed of all nonmanagerial or nonconfidential staff and clerical personnel employed by the judiciary; provided that court officers in the superior court department for Suffolk and Middlesex counties shall be represented by such other bargaining units as they may elect.
The appropriate bargaining unit in the case of employees of the state lottery commission shall be all employees below the rank of assistant director.
Mass. Gen. Laws ch. 150E, § 3