It is, but California's emissions standards have been adopted by other states, and a lot of companies just make one model that is compliant in all 50 states. I'm not sure what the cost difference is these days, but I wonder if it's worth having to maintain two separate lines of inventory. It presents a problem to people who buy a new car, then move to California. If there aren't enough miles on the odometer, California will refuse to register the car because it doesn't meet their emissions standards.