Texas Government Code - GOV'T § 862.002. Membership by Individual

(1) is less than 18 years of age;

(2) is subject to a waiting period under Section 862.0021 for which the governing body of the political subdivision is not making contributions during the waiting period;

(3) does not receive a certification of physical fitness or assignment to perform support services under Section 862.003;  or

(4) is a retiree, regardless of whether the person continues to perform emergency or support services for a department.