Any citizen who has served in the military service of the United States, in the army, navy, or air force thereof, and who has received an honorable discharge therefrom, may be eligible for appointment as a police officer or firefighter in any city or town of this state in the same manner as though that citizen were a qualified elector of the city or town on the date of his or her appointment; provided, however, that the citizen, if registered at any time during the military service, would be a qualified elector of that city or town at the date of that appointment.