Would be nice to be able to do this in Rails 2.3

gistfile1.rb

class Citizen < ActiveRecord::Base  
  contextual :everyone do 
    validates_presence_of :last_name
    validates_format_of :email, :with => /\w+/
  end
  
  contextual :admin do
    validates_presence :first_name
  end
end

class CitizensController < ApplicationController
  def create
    @citizen = Citizen.new params[:citizen]
    if @citizen.save :context => :everyone
      redirect_to @citizen
    else
      render :new
    end
  end
end

class Admin::CitizensController < AdminController
  def create
    @citizen = Citizen.new params[:citizen]
    if @citizen.save :context => :admin
      redirect_to @citizen
    else
      render :new
    end
  end
end