policy.rb

class Policy
  attr_reader :features

  def initialize(defaults=nil)
    if defaults && defaults.respond_to?(:features)
      @features = defaults.features.dup
    else
      @features = {}
    end
  end

  def enable(*feature_names)
    set_features(feature_names, true)
  end

  def disable(*feature_names)
    set_features(feature_names, false)
  end

  def set_features(feature_names, setting)
    [feature_names].flatten.each do |name|
      @features[name.to_sym] = setting
    end

    self
  end

  def method_missing(method_sym, *arguments, &block)
    return super unless method_sym.to_s =~ /\?$/

    feature_name = method_sym.to_s.gsub(/\?$/, '').to_sym

    if @features.key?(feature_name)
      @features[feature_name]
    else
      fail ArgumentError, "Feature: #{feature_name} is not defined in this Policy"
    end
  end
end

p = Policy.new.enable(:derp1, :derp2).disable(:underp1)
puts p.derp1?
puts p.derp2?
puts p.underp1?
begin
  puts p.noderp?
rescue 
  puts 'Exception, nice.'
end

p2 = Policy.new(p).enable(:underp1).disable(:derp2).enable(:noderp)
puts p2.derp1?
puts p2.derp2?
puts p2.underp1?
puts p2.noderp?