Lieber Code of 1863: Section IX and X
148. The law of war does not allow proclaiming either an individual belonging to the hostile army, or a citizen, or a subject of the hostile government an outlaw, who may be slain without trial by any captor, any more than the modern law of peace allows such international outlawry; on the contrary, it abhors such outrage. The sternest retaliation should follow the murder committed in consequence of such proclamation, made by whatever authority. Civilized nations look with horror upon offers of rewards for the assassination of enemies as relapses into barbarism.
SECTION X.—Insurrection—Civil war—Rebellion.
149. Insurrection is the rising of people in arms against their government, or portion of it, or against one or more of its laws, or against an officer or officers of the government. It may be confined to mere armed resistance, or it may have greater ends in view.
150. Civil war is war between two or more portions of a country or state, each contending for the mastery of the whole, and each claiming to be the legitimate government. The term is also sometimes applied to war of rebellion, when the rebellious provinces or portions of the state are contiguous to those containing the seat of government.
151. The term rebellion is applied to an insurrection of large extent, and is usually a war between the legitimate government of a country and portions of provinces of the same who seek to throw off their allegiance to it and set up a government of their own.
152. When humanity induces the adoption of the rules of regular war toward rebels, whether the adoption is partial or entire, it does in no way whatever imply a partial or complete acknowledgment of their government, if they have set up one, or of them, as an independent or sovereign power. Neutrals have no right to make the adoption of the rules of war by the assailed government toward rebels the ground of their own acknowledgment of the revolted people as an independent power.
153. Treating captured rebels as prisoners of war, exchanging them, concluding of cartels, capitulations, or other warlike agreements with them; addressing officers of a rebel army by the rank they may have in the same; accepting flags of truce; or, on the other hand, proclaiming martial law in their territory, or levying war taxes or forced loans, or doing any other act sanctioned or demanded by the law and usages of public war between sovereign belligerents, neither proves nor establishes an acknowledgment of the rebellious people, or of the government which they may have erected, as a public or sovereign power. Nor does the adoption of the rules of war toward rebels imply an engagement with them extending beyond the limits of these rules. It is victory in the field that ends the strife and settles the future relations between the contending parties.
154. Treating in the field the rebellious enemy according to the law and usages of war has never prevented the legitimate government from trying the leaders of the rebellion or chief rebels for high treason, and from treating them accordingly, unless they are included in a general amnesty.
155. All enemies in regular war are divided into two general classes—that is to say, into combatants and non-combatants, or unarmed citizens of the hostile government.
The military commander of the legitimate government, in a war of rebellion, distinguishes between the loyal citizen in the revolted portion of the country and the disloyal citizen. The disloyal citizens may further be classified into those citizens known to sympathize with the rebellion without positively aiding it, and those who, without taking up arms, give positive aid and comfort to the rebellious enemy without being bodily forced thereto.
156. Common justice and plain expediency require that the military commander protect the manifestly loyal citizens in revolted territories against the hardships of the war as much as the common misfortune of all war admits.
The commander will throw the burden of the war, as much as lies within his power, on the disloyal citizens, of the revolted portion or province, subjecting them to a stricter police than the non-combatant enemies have to suffer in regular war; and if he deems it appropriate, or if his government demands of him that every citizen shall, by an oath of allegiance, or by some other manifest act, declare his fidelity to the legitimate government, he may expel, transfer, imprison, or fine the revolted citizens who refuse to pledge themselves anew as citizens obedient to the law and loyal to the government.
Whether it is expedient to do so, and whether reliance can be placed upon such oaths, the commander or his government have the right to decide.
157. Armed or unarmed resistance by citizens of the United States against the lawful movements of their troops is levying war against the United States, and is therefore treason.