California Code, Penal Code - PEN § 71

(a) Every person who, with intent to cause, attempts to cause, or causes, any officer or employee of any public or private educational institution or any public officer or employee to do, or refrain from doing, any act in the performance of his duties, by means of a threat, directly communicated to such person, to inflict an unlawful injury upon any person or property, and it reasonably appears to the recipient of the threat that such threat could be carried out, is guilty of a public offense punishable as follows:

(b) As used in this section, “directly communicated” includes, but is not limited to, a communication to the recipient of the threat by telephone, telegraph, or letter.