Mass. Gen. Laws ch. 127 § 149
If a permit to be at liberty has been revoked, the parole board may order the arrest of the holder of such permit by any officer qualified to serve civil or criminal process in any county, and order the return of such holder to the prison or jail to which he was originally sentenced. A prisoner who has been so returned to prison or jail shall be detained therein according to the terms of his original sentence. In computing the period of his confinement, the time between the day of his release upon a parole permit and the day of issuance of a parole violation warrant shall be considered as part of the term of his original sentence. The time between the day after the issuance of the parole violator warrant until the service of said warrant shall not be considered as any part of the term of his original sentence. Service of the parole violation warrant shall be made effective forthwith upon arrest and imprisonment of the parole violator unless he is convicted of commission of a crime or found guilty of violating the conditions of federal or another state's parole or probation, then service of said parole violation warrant shall not be effective until the expiration of any additional sentences by parole or otherwise. If the parolee is found not guilty of the additional crimes charged or not guilty of violating the conditions of parole or probation then service of the warrant on the parolee shall be made effective on the date of this issuance of said warrant and the time served by him as a result of the parole violation warrant lodged as a detainer shall be considered as part of the original sentence. If the disposition of the new criminal charges or charges of violation of probation or parole is without a finding of guilt, the parole board may retroactively serve the parole violation warrant. The provisions of this section shall not be deemed to preclude the board from withdrawing a parole violation warrant at any time. In computing the period of the parolee's confinement, the time between the day after the issuance of the parole violation warrant until the withdrawal of said warrant shall not be considered as any part of the term of the parolee's original sentence.
Mass. Gen. Laws ch. 127, § 149