California Code, Probate Code - PROB § 19025

(a) If any creditor, beneficiary, or trustee fails timely to file a written pleading upon notice, then the case is at issue, notwithstanding the failure. The case may proceed on the petition and written statements filed by the time of the hearing, and no further pleadings by other persons are necessary. The creditor, beneficiary, or trustee who failed timely to file a written pleading upon notice may not participate further in the proceeding for the determination requested, and that creditor, beneficiary, or trustee shall be bound by the decision in the proceeding.

(b) The court's order, when final, shall be conclusive as to the liability of the trust property with respect to the claims at issue in the petition. In the event of a subsequent administration of the probate estate of the deceased settlor, that order shall be binding on the personal representative of the probate estate of the deceased settlor as well as all creditors and beneficiaries who had notice of the petition.