California Code, Public Utilities Code - PUC § 105153

The district shall recognize and bargain with, as the accredited representative of the employees within the collective bargaining units set forth in Section 105151, the accredited collective bargaining representatives that represent the same or similar bargaining units within the district organized pursuant to Part 3 (commencing with Section 27000) of Division 16 of the Streets and Highways Code.  This recognition shall be maintained unless changed by mutual agreement of the district and the affected collective bargaining representative or the representative is decertified in accordance with the rules and procedures of the Public Employee Relations Board for the certification and decertification of employee representatives.