Miss. Code § 21-31-17
For the benefit of the public service and to prevent delay, injury, or interruption therein by reason of the enactment of Sections 21-31-1 through 21-31-27, all persons holding a position in the fire and/or police departments, including the chief thereof, of any such municipality coming under the provisions of Sections 21-31-1 through 21-31-27, who shall have served continuously in such positions for a period of at least the preceding six months, are hereby declared eligible for permanent appointment under civil service to the offices, positions or employments which they shall then hold, respectively, without examination or other act on their part, and not on probation, and every such person is hereby automatically adopted and inducted permanently into civil service, into such office, place, position or employment which such person then holds as completely and effectually to all intents and purposes as if such person had been permanently appointed thereto under civil service after examination and investigation. However, those persons who have previously left their positions to participate in the armed forces of the United States shall have preference in reemployment and enjoy the rights and privileges of Sections 21-31-1 through 21-31-27 as if their services had not been terminated.
Miss. Code § 21-31-17