Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 54, § 71

The presiding officer at each polling place shall enforce the performance by election officers of their duties. During an election and the counting of the ballots after the close of the polls, he shall have authority to maintain order and to enforce obedience to his lawful commands, in and about the polling place and to keep the access thereto open and unobstructed, and he may require any police officer, constable or other person to communicate his orders and directions and assist in their enforcement.