Only if the gift card value / balance is less than $10. For gift cards with a balance greater than $10, businesses have no obligation to cash them out. However, for gift cards with a balance less than $10, businesses must redeem them for cash (which includes cash, check or bank transfer) when requested by the gift card holder. It is illegal for businesses to refuse this.
Many large businesses have been caught out by this regulation and paid tens of hundreds of thousands in fines and penalties as a result.
Read more about this and other key California gift card laws here.