/** * Processing additional validation to check is carrier applicable. * * @param Mage_Shipping_Model_Rate_Request $request * @return Mage_Shipping_Model_Carrier_Abstract|Mage_Shipping_Model_Rate_Result_Error|boolean */ public function processAdditionalValidation(Mage_Shipping_Model_Rate_Request $request) { // zip code required for US $this->_isZipCodeRequired = $this->_isUSCountry($request->getDestCountryId()); return parent::processAdditionalValidation($request); }