Mil. & Vet. Code, § 146

The Governor may call into active service any portion of the active militia as may be necessary, and if the number available be insufficient, the Governor may call into active service any portion of the unorganized militia as may be necessary, in any of the following events:

(a) In case of war, insurrection, rebellion, invasion, tumult, riot, breach of the peace, public calamity or catastrophe, including, but not limited to, catastrophic fires, or other emergency, or imminent danger thereof, or resistance to the laws of this state or the United States.

(b) Upon call or requisition of the President of the United States.

(c) Upon call of any United States marshal in California, or upon call of any officer of the United States Army commanding an army, army area, or military administrative or tactical command, including generally the State of California, or upon call of any officer of the United States Air Force commanding an air force, air defense force, air defense command, or air command, including generally the State of California.

(d) Upon call of the chief executive officer of any city or city and county, or of any justice of the Supreme Court, or of any judge of the superior court, or of any sheriff, setting forth that there is an unlawful or riotous assembly with intent to commit a felony, or to offer violence to person or property, or to resist the laws of the State of California or the United States or that there has occurred a public calamity or catastrophe requiring aid to the civil authorities.

(e) Upon call of the sheriff setting forth that the civil power of the county is not sufficient to enable the sheriff to execute process delivered to them.