auth.js

const Authenticated = function(isAuthenticated) {
  return React.createClass({
    displayName: 'Authenticated',

    statics: {
      willTransitionTo(transition) {
        if (!isAuthenticated()) {
          transition.redirect('login');
        }
      },
    },

    mixins: [Router.Navigation],

    componentDidUpdate() {
      if (!isAuthenticated()) {
        this.transitionTo('/login');
      }
    },

    render() {
      if (!isAuthenticated()) {
        return <span>'Redirecting to login'</span>;
      }

      return (
        <Router.RouteHandler
          {...this.props}
        />
      );
    },
  });
};