California Code, Probate Code - PROB § 15409

(a) On petition by a trustee or beneficiary, the court may modify the administrative or dispositive provisions of the trust or terminate the trust if, owing to circumstances not known to the settlor and not anticipated by the settlor, the continuation of the trust under its terms would defeat or substantially impair the accomplishment of the purposes of the trust. In this case, if necessary to carry out the purposes of the trust, the court may order the trustee to do acts that are not authorized or are forbidden by the trust instrument.

(b) The court shall consider a trust provision restraining transfer of the beneficiary's interest as a factor in making its decision whether to modify or terminate the trust, but the court is not precluded from exercising its discretion to modify or terminate the trust solely because of a restraint on transfer.