California Code, Elections Code - ELEC § 10308

Within five days after the election, the commissioners shall canvass the returns and declare which persons were elected.  The commission shall issue certificates of election to the persons so declared to be elected.  The certificates shall be signed by all the commissioners, and shall be conclusive evidence of the regularity of all the proceedings taken in the election and by the commission, except as against any suit or proceeding to oust from office any person holding a certificate.