this is a hack

  before :save do
    [
      :contents,
      :venues,
      :states,
      :cities,
      :zips
    ].each do |klass|
      self.send(klass).entries
      many_to_many_model = self.class.relationships[klass].child_model
      unless self.send(klass) == many_to_many_model.all(:publish_group_id => self.id)
        many_to_many_model.all(:publish_group_id => self.id).destroy!
      end
    end
  end