From what I have gathered from the Justice leaders there are a few rules to follow for honorable combat.
Newbie Protection-
No attacking players that have less than 50k Prestige, unless you have less prestige then the certain player. When at war, the minimum is 20k prestige (my opinion). The only other exception is they have been inactive for over 4 days.
Neutral Alliances-
No attacking alliances on your alliance Neutral list. This means they are at a temporary peace treaty.
Valleys-
If someone takes your valley, none of these rules apply to taking it back. Sometimes I will even send one attack to make sure they do not do it again.
Feel free to edit these rules, I do not know them all and this is just from my opinion and what I have been told. Any questions mail your host and they will let you know.
24lbPizza
Host of Justice3