[eluser]CroNiX[/eluser]
You can't protect that dir using htaccess. That only works if you actually visit that dir directly and it appears in the url, which doesn't happen with CI as views are accessed within the controller. You'd need a user auth library or something, and check whether they are logged in or otherwise allowed to view that page via their permissions within the admin controller before allowing them to access the page(s).
You can google "codeigniter user authentication" to find some libraries that have already been created for this purpose.