Mass. Gen. Laws ch. 127 § 86I
The administrator of a county correctional facility may permit an inmate to leave such facility in order to address a public gathering, provided that the administrator receives a request in writing from the sponsor of the public gathering desiring such an address, the inmate is selected after a careful screening process, the inmate leaves the facility in the custody of an officer or employee of the facility and remains in such custody until returned to the facility by said officer or employee, and the sponsor of the public gathering bears the cost of transportation for the inmate and officer.
An inmate shall, at all times during his absence from a correctional facility under this section, be considered as in the custody of the officer having charge of the correctional facility, and the time away from the facility shall be considered as part of the term of the sentence.
Mass. Gen. Laws ch. 127, § 86I