Allegiance (Lat. alligare, to bind to), the subject's duty of obedience to the sovereign under whose protection he is. Allegiance is correlative with protection, and the duty of allegiance is in return for and in consideration of the fact of protection. Therefore, when the sovereign can no longer protect the subject, his allegiance ceases; and on this principle the duty is discharged by conquest or by cession of the sovereign's territory by treaty. Natural allegiance arises from the fact of birth within the territorial domain and actual protection by the sovereign. But actual allegiance is due even by an alien to the sovereign of the state in which he is; though, by comity of nations, there is an exception to this rule in favor of foreign sovereigns and ambassadors and their suites, and of the officers and crews of foreign war ships, and of foreign armies when they are permitted to pass through the state. As allegiance is the highest of the citizen's obligations, so the violation of it is the highest of crimes, or treason.

The principle that allegiance is due to the actual sovereign has been carried so far as to make acts treasons though they were done against a usurper; and Blackstone says that on this ground, after Edward IV. recovered the crown, treasons committed against Henry VI. were capitally punished, though Henry had been declared a usurper by parliament. On the other hand, but on the same principle at common law, and until a statute was passed for their naturalization, the children of English subjects born abroad, that is, out of the king's domain and protection, were aliens. But the most important quality attached by the common law to the doctrine of allegiance was that it was indissoluble. The principle was shortly expressed in the familiar Latin maxim, Nemo potest exuere patriam, "No one can abjure his country," or renounce the fealty which he owes to his sovereign. The maxim is as old as English jurisprudence, and until the most recent period the rule has been maintained in England to its fullest extent.

It has nowhere else been asserted, in modern times at least, with the same rigor with which it was enforced there; and even while it stood the acknowledged rule of the law of England, it was condemned by many of its soundest iu-rists. One of them, Twiss, has very lately said of it that it found no countenance in the law of nations, but was on the contrary in direct conflict with incontestable principles of that system. Observing the more liberal tone of modern public law upon this subject, it is worth notice that it is now asserting only the doctrine which was maintained by the law of Rome in its best period. In his argument for Balbus Cicero declared it to be even the firmest foundation of Roman liberty that the citizen might retain or renounce his allegiance at his pleasure. But the English common law asserted that allegiance intrinsic and absolute arose from the mere fact of birth within the sovereign's dominion and protection; that it could not be cancelled or forfeited by any change of time, place, or circumstances; that the subject could not abjure it or renounce it by abandoning the realm, nor by swearing loyalty to another state; nor could it be released in any way without the concurrence of the supreme legislative power.

Coke expressed the rigor of the rule as it was held in England in his time, and indeed for more than two centuries afterward, when he said that "all subjects are equally bound to their allegiance as if they had taken the oath of it, because it is written by the finger of the law in their hearts." As has just been said, however, this supreme duty might be released by the consent of the sovereign. Such an assent was given, for example, in the case of the United States, when by treaty our independence was recognized by Great Britain; and after that it was several times decided in England that persons, though born here British subjects, who adhered to the new state, ceased to be subjects of the crown and became aliens. But though steadily asserting the rule that allegiance was indissoluble, England has nevertheless practically conceded its invalidity by admitting and naturalizing foreigners into her citizenship, just as all other countries have done. - In modern times at least, no other considerable European state has enforced the theory of the common law, or at least not with the severity with which it was enforced in England. The French code declares expressly that the quality of a Frenchman is lost by naturalization in a foreign country, and France, Spain, and most of the German states have enacted laws regulating the naturalization of foreigners.

The great European authorities in public law, Grotius, Pufendorf, Vattel, and others, concede in general terms the right of expatriation, qualifying it only when it is restrained by law, or when the citizen owes to his native state some already assumed but not yet discharged obligation; if, for example, he has violated the law and owes the penalty, or is invested with some public trust, or war threatens and his sovereign needs his aid; and these have been the chief modifications of the right to renounce allegiance which have been discussed in our own diplomatic correspondence upon this subject with European states. When once naturalization is admitted to be competent and right, the right of expatriation and of renunciation of the former allegiance should seem to be implied as a necessary corollary. Naturalization means the complete adoption of a foreigner and the investing him with the actual citizenship of his adopted country. In practice it compels, as a precedent condition, his entire renunciation of his former allegiance, and the assumption by solemn oath of an exclusive fidelity to the new sovereign; and, with one or two modifications only, it gives him the same rights which he would have had if he had been born within his dominion and protection.

The status which he thus receives is clearly inconsistent with any allegiance to the country of his birth. Allegiance cannot be divided, and if his original allegiance has not been utterly cancelled, then the naturalization is an empty form, and the adopted citizen has not the right to protection and citizenship which the new sovereign pretends to guarantee to him. These considerations have been brought forward in most of the cases which have arisen from time to time in the United States. In the earlier cases, however, though the courts inclined to give them their just weight, they repeatedly evaded direct decision of the question. From an historical review of all the cases which had arisen down to his time, Chancellor Kent declared the prevailing spirit of the decisions to be that, in the absence of any legislation sanctioning the abjuration of allegiance, the rule of the common law remained- unaltered. But in one instance at least, as early as 1812, our government assumed a position on this question quite as advanced as it has ever taken in the cases which have arisen since that time.