"I ended the NAP, I declared WAR, then we went to war as per what the system lets you do. I am not saying it is right or wrong but it is part of the game."
Having a NAP is one thing. If no time was allocated to the cancellation period (ie the time before you can attack, without giving notice), then 'technically' by the rules you've done nothing wrong.
However, a game standard is a 48h nap, but yes that should be specified (ie, some people make it 24h, 72h, or heaps of variations, like "don't explore in these set systems" etc). At least sufficient warning for people to give them a fair chance.
Why? Else you could NAP people, under that pretense. Explore/Gain planets close to them, wait to portal. And then cancel NAP, declare War and attack immediately. And no, not everyone checks Relations Page every tick of the game.
But ofcourse, you're right. These are just norms built into the game by the 'old' players. And its become standardised. It's become unwritten laws which some players abide by. We like to honour them. Ofcourse, you have no technical thing against you, that you 'can' cancel and attack without warning - however it's just frowned upon and people consider it extremely dishonourable.
Why? Cos we play to have fun, and when people take advantage of loopholes (ie, "no time was specified for nap cancellation"), then it pisses people off, and ruins their fun.
It gets annoying when people work hard for their empires/fams - and then it all gets screwed because of a misunderstanding.