California Code, Code of Civil Procedure - CCP § 700.040

(a) Unless another method of levy is provided by this article, to levy upon tangible personal property in the possession or under the control of a third person, the levying officer shall personally serve a copy of the writ of execution and a notice of levy on the third person.

(b) If goods are in the possession of a bailee who has issued a negotiable document of title therefor, the goods may not be levied upon but the negotiable document of title may be levied upon in the manner provided by Section 700.120. If goods are in the possession of a bailee other than one who has issued a negotiable document of title therefor, the goods may be levied upon in the manner provided by Section 700.060. As used in this subdivision, “bailee” means “bailee” as defined in Section 7102 of the Commercial Code.