Cal. PROB § 5023

(a) As used in this section “modification” means revocation of a provision for a nonprobate transfer on death in whole or part, designation of a different beneficiary, or election of a different benefit or payment option. As used in this section, “modification” does not mean, and this section does not apply to, the exercise of a power of appointment under a trust.

(b) If a married person executes a provision for a nonprobate transfer of community property on death with the written consent of the person’s spouse and thereafter executes a modification of the provision for transfer of the property without written consent of the spouse, the modification is effective as to the person’s interest in the community property and has the following effect on the spouse’s interest in the community property:

(1) If the person executes the modification during the spouse’s lifetime, the modification revokes the spouse’s previous written consent to the provision for transfer of the property.

(2) If the person executes the modification after the spouse’s death, the modification does not affect the spouse’s previous written consent to the provision for transfer of the property, and the spouse’s interest in the community property is subject to the nonprobate transfer on death as consented to by the spouse.

(3) If a written expression of intent of a party in the provision for transfer of the property or in the written consent to the provision for transfer of the property authorizes the person to execute a modification after the spouse’s death, the spouse’s interest in the community property is deemed transferred to the married person on the spouse’s death, and the modification is effective as to both the person’s and the spouse’s interests in the community property.