California Code, Financial Code - FIN § 1093

(a) Whenever the officers of a bank are of the opinion that an extraordinary situation exists which affects or may affect one or more of a bank's offices, they shall have the authority in the reasonable and proper exercise of their discretion to determine not to open such offices on any business or banking day, or, if such offices have opened to close one or more of them during the continuation of such extraordinary situation even if the commissioner has not issued and does not issue a proclamation of extraordinary situation. The office or offices so closed shall remain closed until such time as the officers determine with respect to each such office that the extraordinary situation has ended and for such further time thereafter as may reasonably be required to be reopened; however, in no case shall such office or offices remain closed for more than 48 consecutive hours excluding other legal holidays without requesting the approval of the commissioner nor, in case such request is denied by the commissioner, for more than 24 consecutive hours excluding other legal holidays after such denial.

(b) The officers of a bank may close one or more of the bank's offices on any day or days designated for mourning, rejoicing, or other special observance by proclamation of the Governor or the President of the United States.