states.rb

state_machine User do
  state :new
  state :normal
  state :locked
end

state_machine Membership do
  state :new
  state :active
  state :inactive
end

state_machine Account, User do
  # interesting idea... thoughts on this?
end

user.rb

class User
  state_machine do
    state :new
    state :normal
    state :locked
  end
end

This circles around the same problem domain and comes up with a different solution from a different approach: http://www.infoq.com/news/2009/11/restfulie-hypermedia-services

The states are kept in the model, but now we're linking it to the controller and adding some actions via hyperlinking into the resources directly.