protected function createComponentAddUserForm($name)
{
    $form = new AppForm($this, $name);
    $form->...

    $defaults = $this->model->find($this->id);
    $form->setDefaults($defaults);

    // ...
}

public function AddUserFormSubmit($form)
{
    if (!$user->inRole('admin')) {
        throw new BadRequestException();
    }

    // ...
}


// ...

{if $user->inRole('admin')}
    {control addUserForm}
{/if}