Pirating the game and then using your own keys? Illegal as hell, because you'd also still need a crack.
it is against the law to download it from a non authorized distributer (ex: torrent) even if you have a legit set of keys. However, it is a CIVIL and not a CRIMINAL offense... the difference? you will not be arrested for it, but they can sue you and you will have to pay them a lot of money (effectively forcing you to declare bankruptcy).
Any website that allows people to promote such activities likewise is a prime target, this is why most forums ban you for telling someone to get a crack. So, it is against the forum's TOS and can earn you a ban to tell someone to get a copy via a nonlicensed distributer.
This also means you can't use either official patches or premium modules (they authenticate via internet).
All three statements are false.
1. installing official patches (via the auto updater) does even check your keys, it will work regardless.
2. running a premium module only looks at your keys, it will work as long as your key is legitimate, it doesn't know or care what the source of your disk is.
3. while most games would require a no-cd crack, nwn1 has had the CD check removed beginning with patch 1.61 IIRC, it only requires that you have legit keys. thus for nwn1 it will work without a crack.
So, it is against the law, but a civil not criminal offense, it will work, but it is not allowed, and you are risking a virus as well as breaking the law by doing so. so don't do it.