Here's the reply I got from support:
Let's start with how authentication works in Sitefinity. There are two possible situations:You have a user, who's logged in, but doesn't have permissions to see a page. In this case an error of 403 Forbidden is raised.An anonymous user is accessing a page, which is visible for authenticated users only. In this case a 401 Unauthorized error message is generated, which is handled by our source code and results in a 302 response.
The above cases are valid for both Forms and Claims based authentication and their implementation follows the HTTP protocol specification, which can be found here.
In Siteifnity 5.2 there is an event for unauthorized access on front end page, where you can redirect the response depending on your needs. You can take a look on the attached file for an example how to perform the redirect. I hope you will find it useful although it is not just a configuration, but it is much more flexible.
Here's the code from the attached Global.asax:
sender, EventArgs e)
sender, Telerik.Sitefinity.Data.ExecutedEventArgs e)
var url = unauthorizedEvent.Page.Url.TrimStart(