Forcefully logout user from website
Sounds as if you need the Redirect 403 to User Login module:

Redirect the HTTP 403 error page to the Drupal /user/login page with an optional message that reads:
&quot;Access denied! You must login to view this page.&quot;
Also, the desired page is appended in the url query string so that, once login is successful, the user is taken directly where they were originally trying to go.