It might be legal in Cali but they weren't following the guidelines:
"CHP issued guidelines through their California Motorcycle Safety Program in 2017 that instructed motorcyclists to travel no more than 10 miles per hour faster than other traffic and not to lane split when traffic flow is at 30 mph or faster. The guidelines also includes a list of when not to split, disclaimers and messages to other motorists."
No matter, the cops could never/ever catch them, you can't have a car chase if you can't chase the car (or motorcycle).
Treblig
