California Code, Probate Code - PROB § 15403

(a) Except as provided in subdivision (b), if all beneficiaries of an irrevocable trust consent, they may petition the court for modification or termination of the trust.

(b) If the continuance of the trust is necessary to carry out a material purpose of the trust, the trust cannot be modified or terminated unless the court, in its discretion, determines that the reason for doing so under the circumstances outweighs the interest in accomplishing a material purpose of the trust.If the trust is subject to a valid restraint on the transfer of a beneficiary's interest as provided in Chapter 2 (commencing with Section 15300), the trust may not be terminated unless the court determines there is good cause to do so.

(c) If the trust provides for the disposition of principal to a class of persons described only as “heirs” or “next of kin” of the settlor, or using other words that describe the class of all persons who would take under the rules of intestacy, the court may limit the class of beneficiaries whose consent is necessary to modify or terminate a trust to the beneficiaries who are reasonably likely to take under the circumstances.