Never break your word. Never ignore an insult to yourself, a lady, or your flag; insults may only be wiped out by an apology or a duel (not necessarily to the death!). Never take advantage of an opponent in any way; weapons and circumstances must be equal (except in open war). This only applies between gentlemen.
You may fight – you may even start fights – but you may never do anything that seems likely to kill another. This includes abandoning a wounded foe to die “on his own”! You must do your best to keep your companions from killing, too. If you do kill someone (or feel responsible for a death), you immediately suffer a nervous breakdown. Roll 3d and be totally morose and useless for that many days. During this time, you must make a Will roll to offer any sort of violence toward anyone, for any reason.