California Code, Government Code - GOV § 53656

(a) At the time the treasurer enters into a contract with the depository pursuant to Section 53649, he or she shall authorize the agent of depository designated by the depository, but including the trust department of the depository only when acceptable to both the treasurer and the depository, to hold securities of the depository in accordance with this article to secure the deposit of the local agency.

(b) Only those trust companies and trust departments, or the Federal Home Loan Bank of San Francisco, which have been authorized by the administrator pursuant to Section 53657 shall be authorized by treasurers to act as agents of depository.

(c) The securities are subject to order of the depository in accordance with Section 53654 except when the provisions of subdivision (i) of Section 53661 and Section 53665 are in effect.

(d) An agent of depository shall not release any security held to secure a local agency deposit in a depository unless the administrator issues an order authorizing the release where either of the following occurs: