Triggering SP error page / restrict access to a list of users

[Peter Schober]

* Cantor, Scott <cantor.2 at osu.edu> [2011-10-27 16:11]:
> Certainly using user lists doesn¹t scale, no matter how it's handled.

Fyi, http://www.switch.ch/aai/support/tools/gmt.html tries to resolve
that somewhat. Provided email address is known in advance also works
with opaque identifiers (persistentId, ePTId, etc.) unknown to either
the resource owner or the user herself.
-peter