pass variable through segments with security

[eluser]iConTM[/eluser]
Can someone give an example of throwing a 404 with CI?

In the controller class I have something like this:

Code:

function article ($article_id)
{
  $article = $this->model->get_article($article_id);

  if (!$article)
  {
    //throw error 404
    return;
  }

}