California Code, Water Code - WAT § 72150

Territory included within a district may be excluded from the district.  When any part of the corporate area of a city is included in the territory proposed to be excluded from the district, the entire corporate area of the city, or part thereof, then included within the district shall be included in the territory proposed to be excluded from the district except that when the boundaries of the corporate area of a city are also within a metropolitan water district, a portion of such city may be excluded from a district if at the conclusion of the exclusion proceedings such portion of the city will still remain within the boundaries of such metropolitan water district.