The problem with the URL is it's a parameter which causes it to be forbidden. Like:
http://site/Resource?Action=Admin
instead of just:
http://site/Resource
or :
http://site/Resource?Action=Some_legal_action
Which are valid and I do want to be indexed. As far as I've been able to figure out, to exclude the admin actions, I'd have to expose them all in the robots.txt, which is not really something I want.