The California DMV notes that visitors over 18 years old with a valid driver license from their home state or country may drive in California without getting a driver license as long as their home state license remains valid. So as far as state laws go, it would appear that your wife could drive your car with her European license.

As far as your insurance policy covering your wife when she drives your car, it could be a different story. Insurance company's guidelines and policy terms differ so you will need to find out from your specific insurance provider if they will cover your wife if she is driving your car with her foreign license or if they will require her to acquire a CA license to be listed as a driver and covered to drive the vehicle.

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