Sec. 9. MEMBERSHIP. (a) Except as otherwise provided by this section, a person who is an employee of a fire department included within the coverage of a retirement system is a member of the retirement system if the person is younger than 36 years old on the date the person is certified under civil service as eligible for a beginning position with the department.

(b) Except as provided by Subsections (c), (d), (e), and (g) of this section, a person who performs services as a volunteer of a fire department included within the coverage of a retirement system is a member of the retirement system.

(c) A board of trustees established under this Act may, in accordance with Section 7 of this Act:

(1) require a waiting period before retirement system membership begins;

(2) include within the required membership of the retirement system categories of personnel, other than personnel performing services for the fire department, who perform emergency medical or fire department-related services; or

(3) exclude from membership categories of fire department personnel not regularly directly engaged in the fighting of fires.

(d) If a board of trustees, under Subdivision (2) of Subsection (c) of this section, includes categories of personnel within the membership of a retirement system, for purposes of this Act, the personnel are considered employees or volunteers, as applicable, of the fire department and their service is considered as if it were performed for the fire department included within the coverage of the retirement system.

(e) As a condition of membership in a retirement system, a board of trustees may by order require persons to pass a physical examination given by a physician of the board's choice but may not require the persons to pay the cost of the examination.

(f) A board of trustees of a retirement system for a fire department may by order authorize membership in the retirement system for employees of the department who are 36 years old or older at the time they become employees but who first became fire fighters at an age younger than 36. Membership under an authorization is optional with each employee, except that an employee must, before beginning membership, pass any physical examination requirement established under Subsection (e) of this section.

(g) A service retiree of a retirement system may not rejoin or receive credit in the system for any postretirement service performed for the fire department included within the coverage of the system.