California Code, Water Code - WAT § 70038

At the hearing of the formation petition the board of supervisors shall determine whether or not the petition complies with this part and for that purpose shall hear all competent and relevant testimony offered in support of or in opposition thereto. The determination shall be entered upon the minutes of the board of supervisors. A finding of the board of supervisors in favor of the genuineness and sufficiency of the petition and notice shall be conclusive against all persons, except the State in a suit by the Attorney General, commenced within one year after the order of the board of supervisors declaring the district formed.