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.
SDCL 3-12C-306