Mass. Gen. Laws ch. 263A § 7
If a witness, after being offered protective services under this chapter, at any time declines to receive such services, the prosecuting officer shall request that the witness make such refusal in writing, or, if the witness refuses to document such refusal of services in writing, the prosecuting officer shall document the refusal and inform the witness protection board forthwith that the witness has declined protective services. If a witness violates the terms of the memorandum of understanding set forth in section 6 or any other condition of receiving witness protection services under this chapter, the prosecuting officer may revoke and terminate all protective services, and shall so advise the witness in writing. The prosecuting officer shall notify the board forthwith of such revocation and grounds therefore.
Mass. Gen. Laws ch. 263A, § 7