Massachusetts Constitution Pt. 2, Ch. I, § 3, Art. 10

ART. X. The house of representatives shall be the judge of the returns, elections, and qualifications of its own members, as pointed out in the constitution; shall choose their own speaker; appoint their own officers, and settle the rules and orders of proceeding in their own house: They shall have authority to punish by imprisonment, every person, not a member, who shall be guilty of disrespect to the house, by any disorderly, or contemptuous behavior, in its presence; or who, in the town where the general court is sitting, and during the time of its sitting, shall threaten harm to the body or estate of any of its members, for any thing said or done in the house; or who shall assault any of them therefor; or who shall assault, or arrest, any witness, or other person, ordered to attend the house, in his way in going or returning; or who shall rescue any person arrested by the order of the house. And no member of the house of representatives shall be arrested, or held to bail on mesne process, during his going unto, returning from, or his attending the general assembly.