Cannot delete default rule configurations in hook_rules_default_configuration_alter?

@fago thanks very much for the reply.

I'm passing the parameter by reference ( see below ) but it still doesn't appear to remove the default rules, despite clearing all caches with drush cc all

/**
 * hook_default_rules_configuration_alter
 */
function example_default_rules_configuration_alter(&$rules) {

  // These rules are all overridden below with custom versions
  // We need to deactivate the commerce default rules
  if( isset($rules['commerce_checkout_new_account']) ){
    unset($rules['commerce_checkout_new_account']);
  }
  if (isset($rules['commerce_checkout_order_status_update'])){
    unset($rules['commerce_checkout_order_status_update']);
  }
  if (isset($rules['commerce_checkout_order_email'])){
    unset($rules['commerce_checkout_order_email']);
  }
  
}

Is there something else needed there?

DT.

P.S Rules rules :)