galleries_controller.rb

class GalleriesController < ApplicationController
  include GalleriesHelper

  before_filter :find_gallery, :only => [:edit, :show, :update, :destroy]
  before_filter :find_parent, :only => [:new_gallery, :new, :create]

  access_control do
    allow all, :to => [:index, :show]

    allow :admin, :to => [:new_root, :new, :create, :edit, :update, :destroy]
    
    allow :moderator, :of => :gallery,  :to => [:edit, :update, :destroy]
    allow :moderator, :of => :parent,   :to => [:new, :create]
  end
  ...
end