The Policy module provides very little functionality, but is key to the way in which Rampart works. Any user defined policy must use this module, which allows Rampart to find it when your application starts.

Additionally, policies will be given access to functions provided by the main Rampart module, which can be useful if one policy needs to reference rules of another.

The Policy module also defines a behaviour that provides a single callback should_proceed?. By default this will return true, however if implemented, you can return false which will prevent any further authorisation processing. This might seem unusual, but take for example a controller that is restricted to only administrators. Instead of having to test this in every authorisation function, you can simply return false from the should_proceeed?/2 function, and not have to worry about checking later. Much easier.