Recently-announced presidential candidate Marco Rubio was born in the United States but his parents were not U.S. citizens. Does that make him a natural born citizen under the presidential eligibility clause?
My answer is, in a word, yes.
As I (and others) have argued in connection with Ted Cruz's candidacy, the most likely source of the "natural born" phrase in the eligibility clause is English law -- specifically, English law's designation of "natural born subjects." Rubio's case is easier than Cruz's because English common law was clear that birth within sovereign territory was sufficient to make one "natural born." (Cruz's case depends -- although I think convincingly -- on the treatment in English statutory law).
As Blackstone explained (Commentaries, vol. 1, pp. 354-55):
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 ligence, 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 with the king affords the subject. The thing itself, or a 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.
Because the status was "founded in reason and the nature of government" it arose from natural law -- hence "natural" born subject. Later he emphasized that this rule encompassed children of aliens: “[t]he children of aliens, born here in England, are, generally speaking, natural-born subjects, and entitled to all the privileges of such." (Commentaries, vol. 1, pp. 361-62). An exception existed for children of foreign diplomats, but that exception only confirmed the general rule that children of non-diplomat aliens were natural born English subjects if born in England.
A later commentary confirms:
By the common law all persons born within the power or protection of the Crown owe natural allegiance to the King, and are natural-born subjects of the realm, while all born out to the allegiance or protection of the King are aliens born, and remain aliens unless they are subsequently made denizens or naturalized. For the law of England had always adopted to feudal or territorial principle of determining nationality by the place of birth alone.
Henry S.Q. Henriques, The Law of Aliens and Naturalization, p. 29 (1923) (and further, at p. 63: “the general effect [of the common law rule] is, that persons born within the dominions of the King, whether of English or foreign parents, are natural-born subjects, and that persons born without his dominions are aliens.”
There are, as I understand it, two possible counterarguments. First, as discussed in an earlier post, perhaps Blackstone was wrong (that is, wrong about English common law). He might have been (he was wrong about a number of aspects of English law). But I also think that's probably irrelevant. Blackstone is very clear on the point, and to the Framers Blackstone was a definitive account. The meaning of the eligibility clause arises from the way "natural born" was understood in late eighteenth century America, not from what it actually meant in earlier English history.
A second counterargument is that we should not look to Blackstone or English law at all, but rather to continental understandings of natural law, and specifically to Emer de Vattel's 1758 treatise Law of Nations. (See, for example, this law review note, relying on Vattel, and also here). Vattel adopted the common European view (going back at least to Rome) that citizenship turned on ancestry not on the place of birth. The key passage is this one (book I, ch. XIX, § 212) (1797 translation):
The citizens are the members of the civil society: bound to this society by certain duties, and subject to its authority, they equally participate in its advantages. The natives, or natural born citizens, are those born in the country, of parents who are citizens. As the society cannot exist and perpetuate itself otherwise than by the children of the citizens, those children naturally follow the condition of their fathers, and succeed to all their rights. … The country of the fathers is therefore that of the children; and these become true citizens merely by their tacit consent. .. I say, that, in order to be of the country, it is necessary that a person be born of a father who is a citizen; for if he is born there of a foreigner, it will be only the place of his birth, and not his country. [Note that an earlier translation of Vattel, although to the same effect, did not use the phrase "natural born".]
If this is the source of the Framers' understanding, it would be problematic for Rubio; but the evidence tying Vattel to the eligibility clause is thin. It's true that the Framers read Vattel and that he influenced their thinking about the law of nations. But I'm not aware of any surviving evidence of anyone at the time referencing Vattel in connection with the eligibility clause or the phrase "natural born." (Of course, records might have been lost -- in any case there does not seem to have been a broad understanding in this direction.) Further, post-ratification commentary seems instead generally to adopt the Blackstone view. For example, St. George Tucker' s 1803 treatise observes:
Prior to the adoption of the constitution, the people inhabiting the different states might be divided into two classes: natural born citizens, or those born within the state, and aliens, or such as were born out of it. The first, by their birth-right, became entitled to all the privileges of citizens; the second, were entitled to none, but such as were held out and given by the laws of the respective states prior to their emigration.
While some doubts did seem to persist regarding, for example, children born in the United States whose parents were only temporarily present, it seems clear that children whose parents had moved permanently to the United States were broadly considered "natural born" if born there. As a result, the tie to Vattel seems speculative at best, and contrary to the apparent common view in the immediate post-ratification era.
So Rubio's case seems clear to me (but I'm open to counterarguments).