California Code, Vehicle Code - VEH § 23270

(a) No person shall commence to tow any vehicle or other object on any vehicular crossing unless authorized to do so by the Department of Transportation and unless the towing is done by means of a tow truck as defined in Section 615.  No person, other than a member of the California Highway Patrol or an employee of the Department of Transportation, shall, by means of pushing with another vehicle, propel any vehicle or object on a vehicular crossing.  No person, other than an employee of the Department of Transportation, shall, on any vehicular crossing, tow any vehicle or other object except a vehicle or object constructed and designed to be towed by a vehicle of a type similar to that being used for this purpose.

(b) The California Transportation Commission shall, by regulation, establish the maximum towing fee which may be charged by any person authorized to tow a vehicle pursuant to subdivision (a).  No authorized person shall charge a fee for towing a vehicle which is in excess of the maximum fee established by the California Transportation Commission.

(c) The Director of Transportation may grant a special permit to any person to tow any vehicle or object over and completely across any vehicular crossing when in his or her judgment the towing vehicle is so constructed and equipped that the vehicle or object can be towed across the vehicular crossing without endangering persons or property and without interrupting the orderly traffic across the vehicular crossing.

(d) The prohibitions of this section shall apply only on those vehicular crossings upon which a towing service is maintained by the Department of Transportation.