You will need to change over to Arizona insurance and not be able to place your son's AZ registered car on your California insurance policy. This is for a couple of reasons.
One is that your California insurance provider will not likely allow you to insure a car that is registered, driven and garaged out of state with your son. Since he is a college student though your CA insurance company may allow him and the car to be on your policy. Insurance companies' guidelines differ so you would have to check with your insurance agent to see what your insurance carrier's guidelines allow for in this situation.
Even if your insurance carrier guidelines would allow you to insure a car in Arizona for your son attending school, the fact that the car is registered in Arizona does not allow you to use out of state insurance to cover it. This second reason is the main reason that you will not be able to place your CA insurance on your son's AZ registered car.
Arizona is that AZ requires that every motor vehicle operated on our roadways be covered by one of the statutory forms of financial responsibility, more commonly called liability insurance, through a company that is authorized to do business in Arizona. The Arizona Motor Vehicle Department (MVD) notes that out of state insurance is not accepted for Arizona registered cars. All vehicles registered in Arizona must be insured by a company licensed to do business in this state.
One reason that AZ has this law in place is that the minimum requirements for insurance vary by state. For example California and Arizona have different requirement amounts. Minimum levels of financial responsibility in AZ are: $15,000 bodily injury liability for one person and $30,000 for two or more persons and $10,000 property damage liability in AZ. This is referred to as 15/30/10. In California the minimum limits are 15/30/5, so the property damage liability limit for Arizona is double that of CA.
So if you and your son want to keep Arizona registration on the vehicle he buys in AZ then he would need to get an auto insurance policy in AZ. And before deciding to bring the car to California and get it registered in this state you would want to make sure your insurance company would allow you to add the car to your policy since it will be out of state most of the year while your son attending college in Arizona.
The California Department of Insurance notes that if you (or your child) are attending school out of state you will have to give the insurance company the new mailing address and the principal address where the car will be garaged. If your insurance company does not operate in the state where you will be attending college, you will have to get new insurance.
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