[Agema]

There are no hard and fast "rules" regarding NAPs - it's all convention. You can and should be as honourable or treacherous as you like. The trade-off for the advantage of backstabbing is that your reputation, both within the game you're playing and in the general community will suffer. It's up to players to decide whether to take that risk - personally, I think the long term damage is far worse than the short-term gain, but that's me. If players want NAPs to be utterly binding in a game, they should make it a condition of play during the set-up.

The situation listed here is just about the only situation in serious play where I'd think it's not dishonourable to break a NAP. If an opponent is so close to victory that there isn't time to cancel the NAP, by all means launch a sneak attack. You're playing to win, after all. Anyone in the position of being about to win should really be prepared for everyone left to attack at any moment to stop them.