Appellant was arraigned on a felony complaint and made several appearances before a Commissioner. When his preliminary hearing was set before the Commissioner, he filed a written notice of nonstipulation. The Commissioner disallowed his refusal to stipulate, citing a posted notice that all parties are deemed to have stipulated to a Commissioner acting as a temporary judge unless an oral or written objection is made in open court prior to the commencement of the first hearing on the matter. Petitioner filed a petition for writ of mandate. The appellate court here granted the writ, directing the trial court to vacate its order disallowing the refusal to stipulate, and vacating the rule directing forfeiture of the right to a hearing before a judge where a defendant has failed to object at the first hearing in the case. A subordinate judicial officer may serve as a temporary judge only upon the stipulation of the parties, which requires an express or implied stipulation. An implied stipulation arises only where no objection has been made to a hearing which involves the performance of judicial function, such as a trial, sentencing, or preliminary hearing. No stipulation can be implied by participation in a hearing where there is no such function. The trial court’s attempt to create a rule that a party must object prior to the first hearing in the case is without legal foundation.