Forbid Woo checkouts outside of a specific country (using Cloudflare)

functions.php

<?php
// First read: https://support.cloudflare.com/hc/en-us/articles/200168236-Configuring-Cloudflare-IP-Geolocation

function woo_validate_country( $fields, $errors ){
  $countryCode = "RS"; // List of codes: https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2
	if( isset($_SERVER["HTTP_CF_IPCOUNTRY"]) && $_SERVER["HTTP_CF_IPCOUNTRY"] != "" ){
		if( $_SERVER["HTTP_CF_IPCOUNTRY"] != $countryCode && !is_user_logged_in() ){ // ...but allow logged-in users to make orders
			$errors->add( 'validation', 'Error...' ); // <-- Your error message here
		}
	}
}
add_action( 'woocommerce_after_checkout_validation', 'woo_validate_country', 10, 2);