It said natural-born citizens are those defined by natural law. Where is that natural law documented?
Asked and answered. You seem to be a pretty smart person. Citizens are either naturalized, or natural born, right? The OP tells us which are naturalized. The rest are natural born. Documenting who is naturalized takes care of the issue. If you are citizen whose citizenship does not depend on a statute, then you are a natural born citizen. There is plenty of case law dealing with citizenship outside of statute, and in the US, that boils down to jus soli.