I'm probably overlooking something really obvious here.

Comments are in to help explain any library specific code.

public function areCookiesEnabled() {

        $random = 'cx67ds';

        // set cookie
        cookie::set('test_cookie', $random);

        // try and get cookie, if not set to false
        $testCookie = cookie::get('test_cookie', false);


        $cookiesAppend = '?cookies=false';

        // were we able to get the cookie equal ?
        $cookiesEnabled = ($testCookie === $random);

        // if $_GET['cookies'] === false , etc try and remove $_GET portion
        if ($this->input->get('cookies', false) === 'false' AND $cookiesEnabled) {
          url::redirect(str_replace($cookiesAppend, '', url::current())); // redirect 
          return false;
        }

        // all else fails, add a $_GET[]
        if ( ! $cookiesEnabled) {

          url::redirect(url::current().$cookiesAppend);
        }

        return $cookiesEnabled;

    }