Any political subdivision and any public corporation, including municipalities, counties and chartered governmental units in the State of South Dakota, may become a participating unit by a duly passed resolution of its governing body. Any political subdivision not participating in the system on June 30, 1985, may become a participating unit for only its class A members or only its class B members, or for both classes together. If a political subdivision elects to participate for either one class of members or for both classes, all full-time employees in that class or classes shall become members. Source: SL 1961, ch 255 , § 16; SL 1965, ch 220 , § 12; SL 1967, ch 303 , § 10; SDCL §§ 3-12-36, 9-15-24; SL 1968, ch 216 , § 1; SL 1974, ch 35 , § 25; SL 1985, ch 25 ; SDCL § 3-12-67 ; SL 2019, ch 22 , § 1; SL 2021, ch 29 , § 12, eff. Apr. 1, 2021.