Section 41.40.111 - Retirement system employer-Unit of government(1) When a unit of government has become a retirement system employer, all of its employees must be included in the plan membership, if otherwise eligible under this chapter, unless the employee is exempted from membership or qualifies for optional membership pursuant to RCW 41.40.023 or other provision of this chapter.(2) A unit of government which has become a retirement system employer may not withdraw from the retirement system.