The following persons shall become members of the fund:
(1) All active full-time members of a department in service on the day prior to the date of establishment;
(2) All persons who become full-time members on or after the date of establishment who shall become members as a condition of employment, except that, effective July 1, 2013, any member who retires and receives a retirement annuity from the fund shall not be eligible to participate in the fund following retirement and earn a second retirement annuity from the fund; and (3) All members of a department who on the date of establishment are working in a civilian or appointive capacity for the government, the Commonwealth of Kentucky, or the United States of America, while on an approved leave of absence from a department.