How is a policy installed?  Where is it placed?

Each client where the policy will be used will need to install and 'register' the policy.  During the evaluation (or definition), the application needs to know where to find the policy and needs to know which policies are available on the client.

The list of policies is needed so that the admin (dev lead) can choose which policies to install; the user also needs to be able to 'lookup' a policy which the server is aware of.

The policy locations are located in the registry:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\VisualStudio\8.0\TeamFoundation\SourceControl\Checkin Policies

or

HKEY_CURRENT_USER\SOFTWARE\Microsoft\VisualStudio\8.0\TeamFoundation\SourceControl\Checkin Policies

The list of policies is a concatenation of the HKCU and HKLM defined policies.

The value name of this entry is the name of the assembly without the extension.  The value data is the full local path name (with extension).

If a client does not have this policy installed, then the InstallationInstructions will be displayed to the user.  These instructions could then display a link which could install and update the registry appropriately.