With the words “Justice being taken away”, Augustine is qualifying the kind of kingdoms he is talking about. Namely, those kingdoms in which justice has been taken away. The comparison between kingdoms and robberies, then, only applies, in Augustine’s view, if those kingdoms have first abandoned justice. However Augustine does not, in this passage here, say anything about what constitutes injustice. And you cannot conclude that any kingdom that extracts resources under force of law is necessarily unjust, since that extraction may very well be just indeed. Therefore I agree with stickcat that Augustine in this passage is not talking about a just redistribution.