Under subsec 4 of the following statute, one preemptory challenge is allowed (no reason need be given) to have a judge removed. However, if the required stipulation for a commissioner was not stipulated to, that alone is grounds, as is prejudice.
170.6. (a) (1) A judge, court commissioner, or referee of a superior court of the State of California shall not try a civil or criminal action or special proceeding of any kind or character nor hear any matter therein that involves a contested issue of law or fact when it is established as provided in this section that the judge or court commissioner is prejudiced against a party or attorney or the interest of a party or attorney appearing in the action or proceeding. (2) A party to, or an attorney appearing in, an action or proceeding may establish this prejudice by an oral or written motion without prior notice supported by affidavit or declaration under penalty of perjury, or an oral statement under oath, that the judge, court commissioner, or referee before whom the action or proceeding is pending, or to whom it is assigned, is prejudiced against a party or attorney, or the interest of the party or attorney, so that the party or attorney cannot, or believes that he or she cannot, have a fair and impartial trial or hearing before the judge, court commissioner, or referee. If the judge, other than a judge assigned to the case for all purposes, court commissioner, or referee assigned to, or who is scheduled to try, the cause or hear the matter is known at least 10 days before the date set for trial or hearing, the motion shall be made at least 5 days before that date. If directed to the trial of a cause with a master calendar, the motion shall be made to the judge supervising the master calendar not later than the time the cause is assigned for trial. If directed to the trial of a criminal cause that has been assigned to a judge for all purposes, the motion shall be made to the assigned judge or to the presiding judge by a party within 10 days after notice of the all purpose assignment, or if the party has not yet appeared in the action, then within 10 days after the appearance. If directed to the trial of a civil cause that has been assigned to a judge for all purposes, the motion shall be made to the assigned judge or to the presiding judge by a party within 15 days after notice of the all purpose assignment, or if the party has not yet appeared in the action, then within 15 days after the appearance. If the court in which the action is pending is authorized to have no more than one judge, and the motion claims that the duly elected or appointed judge of that court is prejudiced, the motion shall be made before the expiration of 30 days from the date of the first appearance in the action of the party who is making the motion or whose attorney is making the motion. In no event shall a judge, court commissioner, or referee entertain the motion if it is made after the drawing of the name of the first juror, or if there is no jury, after the making of an opening statement by counsel for plaintiff, or if there is no opening statement by counsel for plaintiff, then after swearing in the first witness or the giving of any evidence or after trial of the cause has otherwise commenced. If the motion is directed to a hearing, other than the trial of a cause, the motion shall be made not later than the commencement of the hearing. In the case of trials or hearings not specifically provided for in this paragraph, the procedure specified herein shall be followed as nearly as possible. The fact that a judge, court commissioner, or referee has presided at, or acted in connection with, a pretrial conference or other hearing, proceeding, or motion prior to trial, and not involving a determination of contested fact issues relating to the merits, shall not preclude the later making of the motion provided for in this paragraph at the time and in the manner herein provided. A motion under this paragraph may be made following reversal on appeal of a trial court's decision, or following reversal on appeal of a trial court's final judgment, if the trial judge in the prior proceeding is assigned to conduct a new trial on the matter. Notwithstanding paragraph (4), the party who filed the appeal that resulted in the reversal of a final judgment of a trial court may make a motion under this section regardless of whether that party or side has previously done so. The motion shall be made within 60 days after the party or the party's attorney has been notified of the assignment. (3) A party to a civil action making that motion under this section shall serve notice on all parties no later than five days after making the motion. (4) If the motion is duly presented, and the affidavit or declaration under penalty of perjury is duly filed or an oral statement under oath is duly made, thereupon and without any further act or proof, the judge supervising the master calendar, if any, shall assign some other judge, court commissioner, or referee to try the cause or hear the matter. In other cases, the trial of the cause or the hearing of the matter shall be assigned or transferred to another judge, court commissioner, or referee of the court in which the trial or matter is pending or, if there is no other judge, court commissioner, or referee of the court in which the trial or matter is pending, the Chair of the Judicial Council shall assign some other judge, court commissioner, or referee to try the cause or hear the matter as promptly as possible. Except as provided in this section, no party or attorney shall be permitted to make more than one such motion in any one action or special proceeding pursuant to this section. In actions or special proceedings where there may be more than one plaintiff or similar party or more than one defendant or similar party appearing in the action or special proceeding, only one motion for each side may be made in any one action or special proceeding. (5) Unless required for the convenience of the court or unless good cause is shown, a continuance of the trial or hearing shall not be granted by reason of the making of a motion under this section. If a continuance is granted, the cause or matter shall be continued from day to day or for other limited periods upon the trial or other calendar and shall be reassigned or transferred for trial or hearing as promptly as possible. (6) Any affidavit filed pursuant to this section shall be in substantially the following form: (Here set forth court and cause) State of ss. PEREMPTORY California, CHALLENGE County of ___________ ____, being duly sworn, deposes and says: That he or she is a party (or attorney for a party) to the within action (or special proceeding). That ____ the judge, court commissioner, or referee before whom the trial of the (or a hearing in the) action (or special proceeding) is pending (or to whom it is assigned) is prejudiced against the party (or his or her attorney) or the interest of the party (or his or her attorney) so that affiant cannot or believes that he or she cannot have a fair and impartial trial or hearing before the judge, court commissioner, or referee. Subscribed and sworn to before me this ______ day of ______, 20__. (Clerk or notary public or other officer administering oath) (7) Any oral statement under oath or declaration under penalty of perjury made pursuant to this section shall include substantially the same contents as the affidavit above. (b) Nothing in this section shall affect or limit Section 170 or Title 4 (commencing with Section 392) of Part 2, and this section shall be construed as cumulative thereto. (c) If any provision of this section or the application to any person or circumstance is held invalid, that invalidity shall not affect other provisions or applications of the section that can be given effect without the invalid provision or application and, to this end, the provisions of this section are declared to be severable. 170.7. Section 170.6 does not apply to a judge designated or assigned to serve on the appellate division of a superior court in the judge's capacity as a judge of that division. 170.8. When there is no judge of a court qualified to hear an action or proceeding, the clerk shall forthwith notify the Chairman of the Judicial Council of that fact. The judge assigned by the Chairman of the Judicial Council shall hear the action or proceeding at the time fixed therefor or, if no time has been fixed or good cause appears for changing the time theretofore fixed, the judge shall fix a time for hearing in accordance with law and rules and hear the action or proceeding at the time so fixed.