It is legal to tow a car with a rope in California as long as you're not towing the car on a major highway or freeway.
You can only legally and safely tow a car with a rope in California on less busy roads, back roads or through towns.
It is illegal to tow a car with another car in California on freeways or major highways unless the car or vehicle is attached with a rigid structure and not just a chain or tow strap.
However on smaller roads and through town going at slower speeds it is legal to tow the vehicle or car on the roads in California with another car as long as someone else is guiding the towed vehicle.
If you need to transport a car or vehicle on major highways or freeways then it must be on a tow truck, hooked up to a tow bar or on a trailer.
According to California Vehicle code on towing.
Except as required under paragraph (2), a towed vehicle shall be coupled to the towing vehicle by means of a safety chain, cable, or equivalent device in addition to the regular drawbar, tongue, or other connection.
Using a tow rope to pull a vehicle to another location can be extremely dangerous and should be avoided if possible, particularly if the towed vehicle will not start.
Only tow the vehicle with a tow strap or chain when necessary and only on roads where you won't be going very fast.