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.
William Blackstone, Commentaries 1:354, 357--58, 361--62
1765
no possible under common law, and that is where Blackstone is an authority.
but methinks possible under applicable statutory law which does create dual citizens of many countries....Certainly Blackstone is generally correct, but if statutory laws intervene, then that can be an exception to the general principles of common law....to be continued.