If you are attempting to register a new vehicle (car, truck, van, RV, or motorcycle) from out of state, it must be certified to meet California smog laws in order to obtain registration here. All new vehicles are NOT manufactured to be sold in California. This includes certain model year and weight diesel-powered vehicles. Many automakers design and manufacturer vehicles to be sold only overseas and in states other than California. These vehicles are considered Federal Emissions Complaint (49-state) and are not designed to meet California emissions standards. California-certified (50-state) vehicles on the other hand are made to be sold in California (as well as overseas and other states).
The California Department of Motor Vehicles cannot accept an application to register a vehicle in CA that does not qualify for registration due to emissions certification (H & S Code 43150 - 43156).
The question now becomes... What is Considered a New Vehicle? In California any vehicle with less than 7,500 miles on the odometer at the time of purchase or trade is considered to be "new". And as a new vehicle, it can only be registered in California if its emission systems are configured to be California ARB complaint. This is stands true whether or not the vehicle has been previously be registered in another state.