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Origin: Mid. Eng. ligeaunce; med. Latin ligeantia, &c.; the al- was probably added through confusion with another legal term, allegeance, an allegation; the French allegeance comes from the English; the word is formed from "liege," of which the derivation is given under that heading; the connexion with Latin ligare, to bind, is erroneous.
Allegiance is the duty which a subject or a citizen owes to the state or to the sovereign of the state to which he belongs. It is often used by English legal commentators in a larger sense, divided by them into natural and local, the latter applying to the deference which even a foreigner must pay to the institutions of the country in which he happens to live; but it is in its proper sense, in which it indicates national character and the subjection due to that character, that the word is important. In that sense it represents the feudal liege homage, which could be due only to one lord, while simple homage might be due to every lord under whom the person in question held land. The English doctrine, which was at one time adopted in the United States, asserted that allegiance was indelible: "Nemo potest exuere patriam". Accordingly, as the law stood before 1870, every person who by birth or naturalization satisfied the conditions set forth, though he should be removed in infancy to another country where his family resided, owed an allegiance to the British crown which he could never resign or lose, except by act of parliament or by the recognition of the independence or the cession of the portion of British territory in which he resided. By the Naturalization Act 1870, it was made possible for British subjects to renounce their nationality and allegiance, and the ways in which that nationality is lost are defined. So British subjects voluntarily naturalized in a foreign state are deemed aliens from the time of such naturalization, unless, in the case of persons naturalized before the passing of the act, they have declared their desire to remain British subjects within two years from the passing of the act. Persons who from having been born within British territory are British subjects, but who at birth became under the law of any foreign state subjects of such state, and also persons who though born abroad are British subjects by reason of parentage, may by declarations of alienage get rid of British nationality. Emigration to an uncivilized country leaves British nationality unaffected: indeed the right claimed by all states to follow with their authority their subjects so emigrating is one of the usual and recognized means of colonial expansion.
The doctrine that no man can cast off his native allegiance without the consent of his sovereign was early abandoned in the United States, and in 1868 congress declared that "the right of expatriation is a natural and inherent right of all people, indispensable to the enjoyment of the rights of life, liberty and the pursuit of happiness," and one of "the fundamental principles of the republic" (United States Revised Statutes, sec. 1999). Every citizen of a foreign state in America owes a double allegiance, one to it and one to the United States. He may be guilty of treason against one or both. If the demands of these two sovereigns upon his duty of allegiance come into conflict, those of the United States have the paramount authority in American law.
The oath of allegiance is an oath of fidelity to the sovereign taken by all persons holding important public office and as a condition of naturalization. By ancient common law it might be required of all persons above the age of twelve, and it was repeatedly used as a test for the disaffected. In England it was first imposed by statute in the reign of Elizabeth (1558) and its form has more than once been altered since. Up to the time of the revolution the promise was, "to be true and faithful to the king and his heirs, and truth and faith to bear of life and limb and terrene honour, and not to know or hear of any ill or damage intended him without defending him therefrom." This was thought to favour the doctrine of absolute non-resistance, and accordingly the convention parliament enacted the form that has been in use since that time--"I do sincerely promise and swear that I will be faithful and bear true allegiance to His Majesty . . ."
See also Salmond on "Citizenship and Allegiance," in the Law Quarterly Review (July 1901, January 1902).