This tutorial provides an explanation of how to make state or province field required or not required in Magento.
In order to make state or province field required or not required, you should perform the following:
Open your Admin Panel:
Navigate to System -> Configuration -> General -> State Options:
Select the country(-ies) for which state or province field will be required;
Save the changes by clicking Save Config button:
Feel free to check the detailed video tutorial below: