California Code, Probate Code - PROB § 5305

(a) Notwithstanding Sections 5301 to 5303, inclusive, if parties to an account are married to each other, whether or not they are so described in the deposit agreement, their net contribution to the account is presumed to be and remain their community property.

(b) Notwithstanding Sections 2581 and 2640 of the Family Code, the presumption established by this section is a presumption affecting the burden of proof and may be rebutted by proof of either of the following:

(c) Except as provided in Section 5307, a right of survivorship arising from the express terms of the account or under Section 5302, a beneficiary designation in a Totten trust account, or a P.O.D. payee designation, may not be changed by will.

(d) Except as provided in subdivisions (b) and (c), a multiple-party account created with community property funds does not in any way alter community property rights.