Short answer: Many legal sources, including my own entry in Black’s Law Dictionary (10th ed. 2014), define natural-born citizen as someone who is “born within the jurisdiction.”1 In this phrasing, the term jurisdiction has historically been understood predominantly in its territorial sense. In constitutional contexts, the phrase natural-born citizen has always been contrasted with either alien or naturalized citizen (a foreigner who becomes a citizen). Blood rights are not considered. The common-law meaning of natural-born subject, which is more relevant than the meaning of any post-1789 statute, encompassed the foreign-born child of a subject, as long as the subject-parent was the father.

2. Patriarchal vs. matriarchal lines. Does it matter whether the foreign-born American’s parent having U.S. citizenship was the father or the mother?

Short answer: No. Even if it once mattered (until 1934), the sex of the parent-citizen almost certainly isn’t a factor under current American law. The Supreme Court would today hold that the Fourteenth Amendment’s Equal Protection Clause obliterated any such distinction. Hence a foreign-born American—anyone who is an American at birth as a result of either parent’s citizenship—satisfies the requirements of Article II.

Discussion

The conventional thought is that there are three paths to citizenship: (1) birth within a territory (traditionally known as jus soli); (2) naturalization; and (3) blood rights: the status of being the child of a citizen, even if born outside the territory (traditionally known as jus sanguinis).2 The U.S. Constitution appears to contemplate only the first two categories—not the third, which was created in 1790 by federal statute, one year after the Constitution was ratified.

Before its appearance in the U.S. Constitution, the phrase natural-born citizen was virtually unknown in Anglo-American law. It was analogized from the well-known phrase in English law, natural-born subject (subject being a citizen of a country governed by a monarchy). The two phrases are essentially identical.3 William Blackstone, the most widely read and influential writer on English law when the U.S. Constitution was drafted, had this to say:

The first and most obvious division of the people is into aliens and natural-born subjects. Natural-born subjects are such as are born within the dominions of the crown of England, that is, within the ligeance, or as it is generally called, the allegiance of the king; and aliens, such as are born out of it. Allegiance is the tie, or ligament, which binds the subject to the king, in return for that protection which the king affords the subject. The thing itself, or substantial part of it, is founded in reason and the nature of government; the name and the form are derived to us from our Gothic ancestors.4

Under English statutes, natural-born was extended in meaning over time to cover those born extraterritorially. Originally, only the children of a king’s ambassadors and other diplomats were held to be natural-born subjects, “for as the father, though in a foreign country, owes not even a local allegiance to the prince to whom he is sent; so, with regard to the son also, he was held ... to be born under the king of England’s allegiance, represented by his father, the embassador.”5 In 1352, to encourage foreign commerce, Parliament provided that all children born abroad would be natural-born subjects “provided both their parents were at the time of the birth in allegiance to the king”6—hence both parents had to be English subjects. In 1708 and 1731, the rules were liberalized “so that all children, born out of the king’s ligeance, whose fathers were natural-born subjects, are now natural-born subjects themselves, to all intents and purposes, without any exception.”7