I rearrange the order of the following Epicurean doctrines slightly because I think 33 stands out as the "heading" for all the rest. Thirty-three immediately slaps us in the face, and from it we feel the implications of "there is no such thing as absolute justice." I submit to you that "justice" is simply one of the "virtues," and that Epicurus calls us to read ALL of these doctrines as if the word used were not "justice" but "VIRTUE." (and not "law" but "a code of virtue")
In other words, there is no absolute virtue, and each of these profound statements should be read and absorbed by us as referring to VIRTUE in general:
33. There never was such a thing as absolute justice, but only agreements made in mutual dealings among men in whatever places at various times providing against the infliction or suffering of harm.
34. Injustice is not an evil in itself, but only in consequence of the fear which is associated with the apprehension of being discovered by those appointed to punish such actions.
31. Natural justice is a pledge of reciprocal benefit, to prevent one man from harming or being harmed by another.
32. Those animals which are incapable of making binding agreements with one another not to inflict nor suffer harm are without either justice or injustice; and likewise for those peoples who either could not or would not form binding agreements not to inflict nor suffer harm.
35. It is impossible for a man who secretly violates the terms of the agreement not to harm or be harmed to feel confident that he will remain undiscovered, even if he has already escaped ten thousand times; for until his death he is never sure that he will not be detected.
36. In general justice is the same for all, for it is something found mutually beneficial in men's dealings, but in its application to particular places or other circumstances the same thing is not necessarily just for everyone.
37. Among the things held to be just by law, whatever is proved to be of advantage in men's dealings has the stamp of justice, whether or not it be the same for all; but if a man makes a law and it does not prove to be mutually advantageous, then this is no longer just. And if what is mutually advantageous varies and only for a time corresponds to our concept of justice, nevertheless for that time it is just for those who do not trouble themselves about empty words, but look simply at the facts.
38. Where without any change in circumstances the things held to be just by law are seen not to correspond with the concept of justice in actual practice, such laws are not really just; but wherever the laws have ceased to be advantageous because of a change in circumstances, in that case the laws were for that time just when they were advantageous for the mutual dealings of the citizens, and subsequently ceased to be just when they were no longer advantageous.