login.js

function loggedIn() {
  // ...
}

function requireAuth(nextState, replace) {
  if (!loggedIn()) {
    replace({
      pathname: '/login'
    })
  }
}

function routes() {
  return (
    <Route path="/" component={App}>
      <Route path="login" component={Login} />
      <Route path="logout" component={Logout} />
      <Route path="checkout" component={Checkout} onEnter={requireAuth} />
    </Route>
  );
}

Thanks, and same question from me, How to make store available for lookups? or is there anyway to make getState() be available?

@Gera3dartist FYI, I tested it and it works for me.
https://stackoverflow.com/questions/35849970/accessing-redux-store-from-routes-set-up-via-react-router

But the code need to be change a bit.

export const getRoutes = (store) => {
	const authRequired = (nextState, replaceState) => {
		....
	};
	return (
		<Route path="/" component={App}>
			<Route path="signup" component={SignUp} onEnter={authRequired}/>
		</Route>
	);
};