CA Prob Code Section 3057

(a)

Where a spouse lacks legal capacity and does not have a conservator, any interested person who has knowledge or reason to believe that the rights of such spouse in the community property are being prejudiced may bring an action on behalf of such spouse to enforce the duty imposed by Sections 721 and 1100 of the Family Code with respect to the management and control of the community property and to obtain such relief as may be appropriate.

(b)

If one spouse has a conservator and the other spouse is managing or controlling community property, the conservator has the duty to keep reasonably informed concerning the management and control, including the disposition, of the community property. If the conservator has knowledge or reason to believe that the rights of the conservatee in the community property are being prejudiced, the conservator may bring an action on behalf of the conservatee to enforce the duty imposed by Sections 721 and 1100 of the Family Code with respect to the management and control of the community property and to obtain such relief as may be appropriate.