In prosecuting a foreign war thus duly declared by Congress, we have the right, by “conquest and military occupation,” to acquire possession of the territories of the enemy, and, during the war, to “exercise the fullest rights of sovereignty over it.”  The sovereignty of the enemy is in such case “suspended,” and his laws can “no longer be rightfully enforced” over the conquered territory “or be obligatory upon the inhabitants who remain and submit to the conqueror.  By the surrender the inhabitants pass under a temporary allegiance” to the conqueror, and are “bound by such laws, and such only, as” he may choose to recognize and impose.  “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.”  These are well-established principles of the laws of war, as recognized and practiced by civilized nations, and they have been sanctioned by the highest judicial tribunal of our own country.

The orders and instructions issued to the officers of our Army and Navy, applicable to such portions of the Mexican territory as had been or might be conquered by our arms, were in strict conformity to these principles.  They were, indeed, ameliorations of the rigors of war upon which we might have insisted.  They substituted for the harshness of military rule something of the mildness of civil government, and were not only the exercise of no excess of power, but were a relaxation in favor of the peaceable inhabitants of the conquered territory who had submitted to our authority, and were alike politic and humane.

It is from the same source of authority that we derive the unquestioned right, after the war has been declared by Congress, to blockade the ports and coasts of the enemy, to capture his towns, cities, and provinces, and to levy contributions upon him for the support of our Army.  Of the same character with these is the right to subject to our temporary military government the conquered territories of our enemy.  They are all belligerent rights, and their exercise is as essential to the successful prosecution of a foreign war as the right to fight battles.

New Mexico and Upper California were among the territories conquered and occupied by our forces, and such temporary governments were established over them.  They were established by the officers of our Army and Navy in command, in pursuance of the orders and instructions accompanying my message to the House of Representatives of December 22, 1846.  In their form and detail, as at first established, they exceeded in some respects, as was stated in that message, the authority which had been given, and instructions for the correction of the error were issued in dispatches from the War and Navy Departments of the 11th of January, 1847, copies of which are herewith transmitted.  They have been maintained and supported out of the military exactions and contributions levied upon the enemy, and no part of the expense has been paid out of the Treasury of the United States.