How would I implement this as a named scope?

I've made some fairly simple methods that perform a kind of generic ACL
check. I use it as an initializer that adds one singleton method and
one method to any subclasses of ActiveRecord.

How would I go about changing this algorithm to a named_scope that I
could then use in query chains?

Attachments:
http://www.ruby-forum.com/attachment/3844/ActiveRecord_acl.rb