California Code, Business and Professions Code - BPC § 6211

(a) An attorney or law firm that, in the course of the practice of law, receives or disburses trust funds shall establish and maintain an IOLTA account in which the attorney or law firm shall deposit or invest all client deposits or funds that are nominal in amount or are on deposit or invested for a short period of time. All such client funds may be deposited or invested in a single unsegregated account. The interest and dividends earned on all those accounts shall be paid to the State Bar of California to be used for the purposes set forth in this article.

(b) Nothing in this article shall be construed to prohibit an attorney or law firm from establishing one or more interest bearing bank trust deposit accounts or dividend-paying trust investment accounts as may be permitted by the Supreme Court, with the interest or dividends earned on the accounts payable to clients for trust funds not deposited or invested in accordance with subdivision (a).

(c) With the approval of the Supreme Court, the State Bar may formulate and enforce rules of professional conduct pertaining to the use by attorneys or law firms of an IOLTA account for unsegregated client funds pursuant to this article.

(d) Nothing in this article shall be construed as affecting or impairing the disciplinary powers and authority of the Supreme Court or of the State Bar or as modifying the statutes and rules governing the conduct of licensees of the State Bar.