California Code, Probate Code - PROB § 13051

(a) The guardian or conservator of the estate of a person entitled to any of the decedent's property may act on behalf of the person without authorization or approval of the court in which the guardianship or conservatorship proceeding is pending.

(b) The trustee of a trust may act on behalf of the trust.  In the case of a trust that is subject to continuing jurisdiction of the court pursuant to Chapter 4 (commencing with Section 17300) of Part 5 of Division 9, the trustee may act on behalf of the trust without the need to obtain approval of the court.

(c) If the decedent's will authorizes a custodian under the Uniform Gifts to Minors Act or the Uniform Transfers to Minors Act of any state to receive a devise to a beneficiary, the custodian may act on behalf of the beneficiary until such time as the custodianship terminates.

(d) A sister state personal representative may act on behalf of the beneficiaries as provided in Chapter 3 (commencing with Section 12570) of Part 13 of Division 7.

(e) The attorney in fact authorized under a durable power of attorney may act on behalf of the beneficiary giving the power of attorney.