Since 1995 the California Highway Patrol has taken over all the responsibilities of the California State Police, which no longer exists by that name.
It used to be the case that the Highway Patrol had jurisdiction only on the highways.
“It used to be the case that the Highway Patrol had jurisdiction only on the highways”
Before that they could go anywhere. Then there was the agreement made that the CHP would only cover the highways. There has been some back and forth on this subject over the past 70 years.