Where is the most fitting place for security and roles authorization to fit into the model view presenter design pattern? 

Would it be for all pages that implement security to implement a specific interface, say `IAuthorizedView` that's along the lines of

```
public interface IAuthorizedView : IView
{
    IUser user;
    void AuthorizationInitialized();
    void AuthorizationInvoked();
}

```

Then handled inside the presenter level

```
public abstract class Presenter<TView> where TView : IView
{
    public TView View { get; set; }

    public virtual void OnViewInitialized()
    {
    }

    public virtual void OnViewLoaded()
    {
    }
}

public abstract class AuthorizationSecuredPresenter<TView> 
                        : Presenter<TView> where TView : IAuthorizedView 
{
    public override void OnViewInitialized()
    {
        View.AuthorizationInitialized();
        base.OnViewInitialized();
    }

    public override void OnViewLoaded()
    {
        View.AuthorizationInvoked();
        base.OnViewLoaded();
    }
}

```

This would be my first idea on it, the only question this would leave me is if we move from solely web based and added any type of API that required authorization on the service level that there would end up alot of duplication of access checking or is that perfectly acceptable to verify twice and should be designed for up front?