California Code, Vehicle Code - VEH § 27460

Any passenger vehicle or motortruck having an unladen weight of 6,500 pounds or less and operated and equipped with four-wheel drive and with snow-tread tires on all four drive wheels may be operated upon any portion of a highway without tire traction devices, notwithstanding the fact that the highway is signed for the requirement of those devices and provided that tire traction devices for at least one set of drive wheels are carried in or upon the vehicle. The snow-tread tires shall meet the requirements specified in Section 27459, and the vehicle shall not, when so operated, tow another vehicle except as may be necessary to move a disabled vehicle from the roadway.

No person shall use those tires on four-wheel drive vehicles in place of tire traction devices whenever weather and roadway conditions at the time are such that the stopping, tractive, and cornering abilities of the tires are not adequate or whenever the Department of Transportation or local authorities, in their respective jurisdictions, place signs prohibiting their operation unless equipped with tire traction devices.