“Cite the statutory law, passed in the early days of our Republic, under which YOU qualify for birthright citizenship. You can’t, because it doesn’t exist.”
It was never doubted that the children of citizens born in the country were natural born citizens. They are so without need of any statute.
I see you're helping him out by noting there is no such statute.
So what made such people citizens?
You can say it was "natural law." But there is certainly more than one possible understanding of what "natural law" is.
So there must be some tradition, some accepted rule, that is accepted in the legal circles of the society, that is a LEGAL basis.
That was the common law. And it was put in place, for the most part, because at some point in history a judge sat and made a decision, and that decision was taken as legal precedent.
In fact, the English understanding of natural law, upon which OUR principle of citizenship was based, came from the Bible. England was a Christian nation, and the rulers of that nation adopted the Biblical principle that God had set in place the kingdoms of the world, and one was obliged to be obedient to the lawful governmental authority that God had established.
By that understanding, NATURAL LAW meant that if you were born into a kingdom, or under a king, you were a member of that kingdom and obliged to be obedient to that king, as long as he gave directives that didn't violate divine law. Even if he was generally a bad king, you were still obliged to obey legitimate laws.
But you, and the other denialists, deny this natural-law based principle that we inherited in our law from our heritage as English colonies.