There is certain behaviour expected when in a NAP with another group;
1. No probing of planets with whom we have NAP's, this does not include sending recyclers to debris fields.
2. Obviously no attacking of planets/fleets of NAP groups.
3. Just because we have a NAP with someone doesnt mean we have to back them up in a war, this would be on an individual basis within the alliance.
Will add more as I think of it - but thats the basics covered