Mass. Gen. Laws ch. 123B § 6
Pursuant to departmental regulations on admission procedures, the superintendent may receive and retain on a voluntary basis any person with an intellectual disability providing the person is in need of care and treatment and providing the admitting facility is suitable for such care and treatment. The application may be made (1) by a person who has attained the age of sixteen, (2) by a parent or guardian of a person on behalf of a person under the age of eighteen years, and (3) by the duly authorized guardian of a person on behalf of an adult person under his guardianship. Prior to accepting an application for a voluntary admission, the superintendent shall afford the person making the application the opportunity for consultation with an attorney, or with a person who is working under the supervision of an attorney, concerning the legal effect of a voluntary admission. The superintendent may discharge any person admitted under the provisions of this paragraph at any time he deems such discharge in the best interest of such person, provided, however, that if a parent or guardian made the application for admission, fourteen days' notice shall be given to such parent or guardian prior to such discharge.
Mass. Gen. Laws ch. 123B, § 6