Section 21715 Of Article 2. Additional Driving Rules From California Vehicle Code >> Division 11. >> Chapter 3. >> Article 2.

. (a) No passenger vehicle regardless of weight, or any other motor vehicle under 4,000 pounds unladen, shall draw or tow more than one vehicle in combination, except that an auxiliary dolly or tow dolly may be used with the towed vehicle.
  (b) No motor vehicle under 4,000 pounds unladen shall tow any vehicle weighing 6,000 pounds or more gross.