Mich. Comp. Laws § 32.49
Notwithstanding any other provisions of this act any officer of the national guard, including also the adjutant general of the state, who shall have completed not less than 15 years service and who is not less than 64 years of age and who is or has been on actual state duty for not less than 10 years, may be retired with annual pay equal to the product of 2 and 1/2 per centum of the active service annual pay to which entitled at the time of his retirement multiplied by a number equal to the years of his active service, not in excess of 30 years: Provided, That the number of years of service to be credited in computing the right to retirement pay shall include all service for or hereafter credited for active duty pay purposes: Provided, That any fractional part of a year amounting to 6 months or more to be counted as a complete year: And provided further, That any officer retired before the completion of 30 years commissioned service may be employed on such active duty as he may be capable of performing until he has completed 30 years commissioned service or reached 64 years of age. Any other officer who shall have completed not less than 15 years service and who is not less than 64 years of age may be retired with annual pay of 480 dollars. Any such officer, when retired under the provisions hereof, shall be eligible for detail to any court constituted under orders of the governor, and for any other specific temporary duty not involving the command of troops, or in an advisory capacity, for periods of not to exceed 15 days without his consent, upon orders of the governor, with pay and allowances of his rank when retired, in any case: Provided, That his retired pay and allowances shall stand suspended during such time as he shall be serving on such actual duty. Any enlisted man who shall have completed not less than 15 years service and who is not less than 64 years of age may be retired with annual pay of 180 dollars.
MCL 32.49