California does recognize a valid driver license that is issued by a foreign jurisdiction (country, state, territory) of which the license holder is a resident.
If you are a visitor in California over 18 and have a valid driver license from your home state or country, you may drive in this state without getting a California driver license as long as your home state license remains valid.
What if the driver holds a driving license from a foreign country of which they're not resident (i.e. they're resident of yet another foreign country)? Does this mean they cannot use that license to drive in California?