Policies allow you to define the same policy twice - once with ALLOW and once with DENY

To replicate start wookie and goto the polices part of the admin section (viewwhitelist.jsp).
Notice how the weather widgets policy is already there...

http://www.getwookie.org/widgets/weather http://newsrss.bbc.co.uk:80 ALLOW

Next in the box 'add a policy' below the list add the following to change this entry to denied

http://www.getwookie.org/widgets/weather http://newsrss.bbc.co.uk:80 DENY

I would expect the original entry to update, but instead there are now two entries for the same policy.