Mass. Gen. Laws ch. 33 § 31
An officer or noncommissioned officer in the armed forces of the commonwealth at the age of 65 shall be honorably discharged or, upon request by such officer and pursuant to the eligibility requirements of this section, placed upon the retired list with the highest grade held in the active military service.
A member of the army or air national guard of the commonwealth, with at least a total of 20 years of service as an officer or noncommissioned officer in the army or air national guard of the commonwealth or the uniformed services of the United States, of which at least the last 5 years of service shall have been in the army or air national guard of the commonwealth or the state staff, shall be placed upon the retired list with any grade held by the member in the active military service or 1 grade higher, but not to exceed the grade of major general; provided, however, that any such member who has had federal recognition in the grade of major general may, upon request, be placed upon the retired list in the grade of lieutenant general.
Members of the armed forces of the commonwealth on the retired list accepting appointment to or a commission in the active military forces of the commonwealth may again be placed upon said retired list, at their own request.
Mass. Gen. Laws ch. 33, § 31