Albrecht wrote
google knows about this pages and gives access. Why this?
What does "gives access" mean. When you click a search result you can see the page, even though you're logged in?
Google can not index what it can't see. Google spiders anonymously (it has no login to your site) unless you explicitly gave it a non-anonymous access (eg. by putting a link with user and password somewhere publically).
It might be that these pages once were unprotected and thus spidered by Google and even though they are now protected are still in the Index.