Cal. Pub. Util. Code § 29719.5

If the board finds that protest has been made, prior to the board’s final determination for annexation, by the owners of real property within the area to be annexed the assessed value of which, as shown by the last equalized assessment roll, constitutes more than one-half of the total assessed value of the real property within the area to be annexed, the proceeding shall terminate. The board shall order the proceedings terminated when such protests are received.