Wait a second

A lawful neutral character acts as law, tradition, or a personal code directs her.
I have to read things closer. Really, the description of LN has a personal code in it!? It uses the that "or" connector too. So I'm not sure a personal code of honor is the most helpful part of societal cohesion, but its right there in the description of lawfulness.

Still, reading the whole SRD clearly indicates that there is more than just a "pick your code" that this quote might indicate. A lawful character from the description of lawfulness, wants societal order and generally respects authority.