California Code, Vehicle Code - VEH § 13801

In addition to the investigation, the department may require the re-examination of the licensee, and shall give 10 days' written notice of the time and place thereof. If the licensee refuses or fails to submit to the re-examination, the department may peremptorily suspend the driving privilege of the person until such time as the licensee shall have submitted to re-examination. The suspension shall be effective upon notice.