Only a--reasonably and relatively; no society is perfect--just and civil society provides (over a sufficiently long time horizon) the kind of stability and structure that allows the rich to stay rich. Which doesn't mean that you can't get rich in other societies, of course. But, broadly and historically speaking, having to expend those riches directly on men who will harm and kill for you has something of an expiration date, usually around when they realize they can just take more than you'd be paying them.

That's to say that functional courts and a state that acts as the only legitimate applicator of force tends to be a lot better for the rich, and those too fall (or themselves turn on the rich, too) when they stray too far from the line.