The 14th amendment is an executive order (proclamation) Vol. 1 of Presidential Executive Orders, 2 vols. (N.Y.: Books, Inc. 1944—Copyright by Mayor of N.Y. 1944).
“[T]he term 'subject to the jurisdiction thereof' . . . must be construed in the sense in which the term is used in international law as accepted in the United States as well as Europe. * * * The provision of the 14th Amendment alluded to [i.e., 'subject to the jurisdiction thereof'] . . . is affirmative and declaratory, intended to allay doubts and to settle controversies which had arisen with respect to citizenship.” Francis Wharton, A Treatise on the Conflict of Laws or Private International Law, 3rd ed. (Lawyers Co-operative Publishing Co., 1906), Vol. 1, pp. 45-47.