How to block Bittorrent for everyone:
You need to have the Policy Enforcement License Installed (you do) You would then need to edit the Global SaCL ACL to block bittorrent:
Go to Configuration> Security> Access Control> Policies Tab. Edit the "Global-Sacl" firewall policy. This is the firewall policy that applies to everyone.
Click on Add and Select the options like the screenshot:
Click on Add on the right, then click on Apply. Click on "save configuration" at the top to make sure it is pushed to all of your locals. This should block peer to peer traffic for everyone.
Note: If someone is currently bittorrenting, it will not stop them, only if they attempt to start a session.