Prices by Country - Make products unavailable for a region

<?php
/**
 * Aelia Prices by Country customisation.
 * Makes all products unavailable for a specific region.
 *
 * NOTE
 * Customisations, such as this one, are outside the scope of Aelia's support
 * service. If you need assistance to implement, or alter this custom code,
 * you can hire us on Codeable: http://bit.ly/codeable_discount_new
 *
 * @param bool purchasable The original "purchasable" flag.
 * @param WC_Product product The product to process.
 * @return bool
 * @author Aelia
 */
add_filter('woocommerce_is_purchasable', function($purchasable, $product) {
  // Get the instance of the Prices by Country plugin
  $pbc = \Aelia\WC\PricesByCountry\WC_Aelia_Prices_By_Country::instance();
  // Get the ID of the region to which customer's country belongs
  $region_id = $pbc->settings_controller()->get_region_for_country($pbc->get_customer_country());

  // Find the region ID from WooCommerce > Prices by Country settings page
  // Example: http://prntscr.com/cvxfg6
  $disabled_region_id = '<region ID here>';

  if($region_id === $disabled_region_id) {
    $purchasable = false;
  }
  return $purchasable;
}, 50, 2);