The board may contract with the Board of Administration of the Public Employees' Retirement System or with a retirement system maintained pursuant to the County Employees Retirement Law of 1937 and enter all, or any portion, of its employees under either of those systems. Employees of the district in a bargaining unit that is represented by a labor organization shall not be included in the contract except as authorized by a collective bargaining agreement.
Ca. Pub. Util. Code § 105171