Mere conquest, that is, the occupation by military force of foreign territory, is not sufficient to annex such territory to the State whose forces are in possession of it. However, for the time being, as a belligerent right, and from necessity, the entire control of this area, its government, and the life and property of its inhabitants are in the hands of the victorious power. The inhabitants are no longer protected by the State whose forces have been ousted, and for the time being owe no allegiance to it, but owe an allegiance to the State which is in possession.
In the quite early case of United States v. Rice1 the doctrine of military possession is discussed with reference to the port of Castine, Maine, which, for a time during the War of 1812, was in possession of the British military forces, but after peace was restored, and returned to the United States. The court say: "It appears, by the pleadings, that on the first day of September, 1814, Castine was captured by the enemy, and remained in his exclusive possession, under the command and control of his military and naval forces, until after the ratification of the treaty of peace in February, 1815. . . . By the conquest and military occupation of Castine, the enemy acquired that firm possession which enabled him to exercise the fullest rights of sovereignty over that place. The sovereignty of the United States over the territory was, of course, suspended, and the laws of the United States could no longer be rightfully enforced there, or be obligatory upon the inhabitants who remained and submitted to the conquerors. By the surrender the inhabitants passed under a temporary allegiance to the British Government, and were bound by such laws, and such only, as it chose to recognize and impose.
1 4 Wh. 246; 4 L. ed. 562.
From the nature of the case, no other laws could be obligatory upon them, for where there is no protection or allegiance or sovereignty, there can be no claim to obedience. Castine was, therefore, during this period, so far as respected our revenue laws, to be deemed a foreign port; and goods imported into it by the inhabitants were subject to such duties only as the British Government chose to require. Such goods were in no correct sense imported into the United States. The subsequent evacuation by the enemy, and resumption of authority by the United States, did not, and could not, change the character of the previous transactions."
In Fleming v. Page2 the question arose whether duties levied upon goods entering the United States from the port of Tampico, at the time it was in the military possession of the United States, were properly levied under the Act of Congress which imposed duties upon goods imported from a foreign country. Taney, who rendered the opinion of the court, said: "The Mexican authorities had been driven out, or had submitted to our army and navy and the country was in the exclusive and firm possession of the United States and governed by the military authorities, acting under the orders of the President. But it docs not follow that it was a part of the United States, or that it ceased to be a foreign country, in the sense in which these words are used in the acts of Congress. The country in question had been conquered in war. But the genius and character of our institutions are peaceful and the power to declare war was not conferred upon Congress for the purposes of aggression or aggrandizement, but to enable the General Government to vindicate by arms, if it should become necessary, its own rights and the rights of its citizens. A war, therefore, declared by Congress can never be presumed to be waged for the purpose of conquest or the acquisition of territory; nor does the law declaring the war imply an authority to the President to enlarge the limits of the United States by subjugating the enemy's territory. The United States, it is true, may enlarge its boundaries by conquest or treaty and may demand the cession of territory as a condition of peace in order to indemnify its citizens for the injuries they have suffered, or to reimburse the government for the expense of the war; but this can be done only by the treaty-making power or the legislative authority, and is not a part of the power conferred upon the President by the declaration of war. His duty and power are purely military. . . . He may invade the hostile country and subject it to the sovereignty and authority of the United States; but his conquests do not enlarge the boundaries of this Union nor extend the operations of our institutions and laws beyond the limits before assigned to them by the legislative power. It is true, that, when Tampico had been captured, and the State of Tamaulipas subjugated, other nations were bound to regard the country, while our possession continued, as the territory of the United States, and to respect it as such. For, by the laws and usages of nations, conquest is a valid title, while the victor maintains the exclusive possession of the conquered country. The citizens of no other nation, therefore, had a right to enter it without the permission of the American authorities, nor to hold intercourse with its inhabitants, nor to trade with them. As regarded all other nations, it was a part of the United States, and belonged to them as exclusively as the territory included in our established boundaries. But yet it was not a part of this Union. For every nation which acquires territory by treaty or conquest, holds it according to its own institutions and laws. And the relation in which the port of Tampico stood to the United States while it was occupied by their arms did not depend upon the laws of nations, but upon our own Constitution and acts of Congress. The power of the President under which Tampico and the State of Tamaulipas were conquered and held in subjection was simply that of a military commander prosecuting a war waged against a public enemy by the authority of his government. And the country from which these goods were imported was invaded and subdued, and occupied as the territory of a foreign hostile nation, as a portion of Mexico, and was held in possession in order to distress and harass the enemy. While it was occupied by our troops, they were in an enemy's country, and not in their own; the inhabitants were still foreigners and enemies, and owed to the United States nothing more than the submission and obedience, sometimes called temporary allegiance, which is due from a conquered enemy, when he surrenders to a force which he is unable to resist. But the boundaries of the United States, as they existed when war was declared against Mexico, were not extended by the conquest; nor could they be regulated by the varying incidents of war, and be enlarged or diminished as the armies on either side advanced or retreated. They remained unchanged. And every place which was out of the limits of the United States, as previously established by the political authorities of the government, was still foreign; nor did our laws extend over it. Tampico was, therefore, a foreign port when this shipment was made."
2 9 How. C03; 13 L. ed. 276.