California Code, Water Code - WAT § 11584

No water which, prior to January 13, 1934, was appropriated, or for which application has been filed prior to January 13, 1934, and remains in good standing, nor any tunnels, canals, dams, and appurtenant works dedicated to public use prior to July 1, 1933, may be acquired by the department through eminent domain proceedings except, unless and until it is first determined in a court of competent jurisdiction that the use proposed to be made thereof by the department is a more necessary public use than that to which it has already been appropriated or dedicated.