authenticated_route.js

ItemManager.AuthenticatedRoute = Ember.Route.extend({
  beforeModel: function(transition) {
    if (!this.controllerFor('sign_in').get('user')) {
      this.redirectToSignIn(transition);
    }
  },

  redirectToSignIn: function(transition) {
    var signInController= this.controllerFor('sign_in');
    signInController.set('attemptedTransition', transition);
    this.transitionTo('sign_in');
  },

  actions: {
    error: function(reason, transition) {
      if (reason.status == 401) {
        this.redirectToSignIn(transition);
      } else {
        alert('Something went wrong');
      }
    }
  }
});

ItemManager.SignInRoute = Ember.Route.extend({
  setupController: function(controller) {
    controller.reset();
  }
});

ItemManager.SignUpRoute = Ember.Route.extend({
  setupController: function(controller) {
    controller.reset();
  }
})

sign_in_controller.js

ItemManager.SignInController = Ember.Controller.extend({
  needs: ['application'],
  showDropdown: Ember.computed.alias('controllers.application.showDropdown'),

  user: function(key, val) {
    if (arguments.length > 1) {
      localStorage.setItem('user', JSON.stringify(val));
      return val;
    }
    var rawUser = localStorage.getItem('user');
    if(typeof rawUser === null){
      return null;
    } else {
      return JSON.parse(rawUser);  
    }
  }.property(),

  actions: {
    login: function() {
      var _this = this,
          data = {user: this.getProperties('email', 'password')};

      _this.set('errorMessage', null);
      $.post('/users/sign_in', data)
        .success(function(response) {
          _this.set('user', response.user_session);
          var attemptedTransition = _this.get('attemptedTransition');
          if (attemptedTransition) {
            attemptedTransition.retry();
            _this.set('attemptedTransition', null);
          } else {
            _this.transitionToRoute('projects.index');
          }
        }).error(function(response) {
          _this.set('errorMessage', response.responseText);
        });
    },
    logout: function(){
      // TODO: This should issue a `DELETE /users/sign_out` request to the server
      this.setProperties({
        user: null,
        showDropdown: false
      });
      delete localStorage.user;
      this.transitionToRoute('sign_in');
    }
  },

  reset: function() {
    this.setProperties({
      email: "",
      password: "",
      errorMessage: ""
    });
  }
});

How are you actually using AuthenticatedRoute? I mean, how do you actually use it in your router.js?