California Vehicle Code Section 15306

(a) A driver may not operate a commercial motor vehicle for a period of 60 days if the person is convicted of a serious traffic violation involving a commercial motor vehicle and the offense occurred within three years of a separate offense of a serious traffic violation that resulted in a conviction. (b) A driver may not operate a commercial motor vehicle for a period of 60 days when the person is convicted of a serious traffic violation involving a noncommercial motor vehicle, if the conviction for the offense resulted in the revocation, cancellation, or suspension of the driver`s license, and the offense occurred within three years of a separate offense of a serious traffic violation that resulted in a conviction. (c) This section shall become operative on September 20, 2005.