Assuming you're using Django's built-in redirect app
(http://docs.djangoproject.com/en/dev/ref/contrib/redirects/), it's
the later: that app doesn't redirect away from pages that exist.
From the docs: "Each time any Django application raises a 404 error,
this middleware checks the redirects database for the requested URL as
a last resort." Notice that this only happens when an application's
already raised a 404 error, i.e. already reported an invalid URL.
Jacob