Ok this moves us as expected into the area of interpreting "natural justice."
Do we all here agree that there is no absolute standard of natural justice? And that the "harmed or be harmed" reference is simply something similar to a statement of virtue, which much be translated into the "pleasure" of the people involved? And that when the individuals no longer agree on their pleasures, there is no longer any natural justice involved in the issue of "harmed or be harmed"?
I suspect that in this discussion so far everyone will largely agree that the answer to that question is "yes, there is no absolute justice" - but probably not without hesitation. I think in most all discussions of this we find that this is one of the least discussed areas of the PDs because many people do not want to see the clear statement here that Epicurus is saying that no individual's version of "justice" is applicable to all times and all people and all places. And of course since most people are dedicated to their pre-existing absolute standards of "virtue" they find these impossible to accept as written. The temptation is therefore to think that there is an absolute standard of "harm or be harmed" but that is not likely at all to be the case given the nature of the Epicurean universe, where there are no absolute standards other than the pleasure and pain of the people involved, correct?
33. Justice never is anything in itself, but in the dealings of men with one another, in any place whatever, and at any time, it is a kind of compact not to harm or be harmed.
34. Injustice is not an evil in itself, but only in consequence of the fear which attaches to the apprehension of being unable to escape those appointed to punish such actions.
35. It is not possible for one who acts in secret contravention of the terms of the compact not to harm or be harmed to be confident that he will escape detection, even if, at present, he escapes a thousand times. For up to the time of death it cannot be certain that he will indeed escape.
36. In its general aspect, justice is the same for all, for it is a kind of mutual advantage in the dealings of men with one another; but with reference to the individual peculiarities of a country, or any other circumstances, the same thing does not turn out to be just for all.
37. Among actions which are sanctioned as just by law, that which is proved, on examination, to be of advantage, in the requirements of men's dealings with one another, has the guarantee of justice, whether it is the same for all or not. But if a man makes a law, and it does not turn out to lead to advantage in men's dealings with each other, then it no longer has the essential nature of justice. And even if the advantage in the matter of justice shifts from one side to the other, but for a while accords with the general concept, it is nonetheless just for that period, in the eyes of those who do not confound themselves with empty sounds, but look to the actual facts.
38. Where, provided the circumstances have not been altered, actions which were considered just have been shown not to accord with the general concept, in actual practice, then they are not just. But where, when circumstances have changed, the same actions which were sanctioned as just no longer lead to advantage, they were just at the time, when they were of advantage for the dealings of fellow-citizens with one another, but subsequently they are no longer just, when no longer of advantage.