The meaning of "natural born."

I read with some amusement the struggles that some non-lawyers [and some lawyers as well] have been having understanding the language of Art II, Sec. 1 of the U.S. Constitution: "No Person except a natural born Citizen, or a Citizen of the United States, at the time of the Adoption of this Constitution, shall be eligible to the Office of President . . . ." If the drafters of the Constitution had wanted to require that presidents be born in the United States, they could have done so. Instead, they invoked the then-standard idea of natural citizenship as reflecting natural allegiance to the king or the state.

Standard 18th century dictionaries and commentaries couldn’t have been clearer on this point. For example, Giles Jacob in The New Law-Dictionary (1743) and The Common Law Common-plac’d (1733) made clear who was an alien and who was a "natural born subject”:

The Children of Ambassadors in a foreign Country, are natural born Subjects, and not Aliens. Id. at 22 (Eighteenth Century Collections Online)

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Blackstone has a lengthy treatment:

William Blackstone, Commentaries 1:354, 357--58, 361--62 (1765)

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 ligamen, 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.

. . . . .

Allegiance, both express and implied, is however distinguished by the law into two sorts or species, the one natural, the other local; the former being also perpetual, the latter temporary. Natural allegiance is such as is due from all men born within the king's dominions immediately upon their birth. For, immediately upon their birth, they are under the king's protection; at a time too, when (during their infancy) they are incapable of protecting themselves.

Natural allegiance is therefore a debt of gratitude; which cannot be forfeited, cancelled, or altered, by any change of time, place, or circumstance, nor by any thing but the united concurrence of the legislature. An Englishman who removes to France, or to China, owes the same allegiance to the king of England there as at home, and twenty years hence as well as now. For it is a principle of universal law, that the natural-born subject of one prince cannot by any act of his own, no, not by swearing allegiance to another, put off or discharge his natural allegiance to the former: for this natural allegiance was intrinsic, and primitive, and antecedent to the other; and cannot be devested without the concurrent act of that prince to whom it was first due. Indeed the natural-born subject of one prince, to whom he owes allegiance, may be entangled by subjecting himself absolutely to another; but it is his own act that brings him into these straits and difficulties, of owing service to two masters; and it is unreasonable that, by such voluntary act of his own, he should be able at pleasure to unloose those bands, by which he is connected to his natural prince.

Local allegiance is such as is due from an alien, or stranger born, for so long time as he continues within the king's dominion and protection: and it ceases, the instant such stranger transfers himself from this kingdom to another. Natural allegiance is therefore perpetual, and local temporary only: and that for this reason, evidently founded upon the nature of government; that allegiance is a debt due from the subject, upon an implied contract with the prince, that so long as the one affords protection, so long the other will demean himself faithfully. As therefore the prince is always under a constant tie to protect his natural-born subjects, at all times and in all countries, for this reason their allegiance due to him is equally universal and permanent. But, on the other hand, as the prince affords his protection to an alien, only during his residence in this realm, the allegiance of an alien is confined (in point of time) to the duration of such his residence, and (in point of locality) to the dominions of the British empire.

. . . . .

When I say, that an alien is one who is born out of the king's dominions, or allegiance, this also must be understood with some restrictions. The common law indeed stood absolutely so; with only a very few exceptions: so that a particular act of parliament became necessary after the restoration, for the naturalization of children of his majesty's English subjects, born in foreign countries during the late troubles. And this maxim of the law proceeded upon a general principle, that every man owes natural allegiance where he is born, and cannot owe two such allegiances, or serve two masters, at once. Yet the children of the king's embassadors born abroad were always held to be natural 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 (by a kind of postliminium) to be born under the king of England's allegiance, represented by his father, the embassador.

To encourage also foreign commerce, it was enacted by statute 25 Edw. III. st. 2. that all children born abroad, provided both their parents were at the time of the birth in allegiance to the king, and the mother had passed the seas by her husband's consent, might inherit as if born in England: and accordingly it hath been so adjudged in behalf of merchants. But by several more modern statutes these restrictions are still farther taken off: 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; unless their said fathers were attainted, or banished beyond sea, for high treason; or were then in the service of a prince at enmity with Great Britain.

According to even the most technical meaning of "natural born" citizen in the 1780s, John McCain is a natural born citizen of the United States, but George Washington and Thomas Jefferson may not have been (since they were born before 1776), though they would have been generally treated as such at the time.