Soldiers have rights, insofar as they are members of the armed forces, as defined in international humanitarian law (IHL). They are known as combatants and have the right to participate directly in hostilities. This means, in practical terms, that combatants are entitled to attack enemy forces, kill or injure them, and destroy property as part of military operations—activities that if done not in wartime or not by combatants would all be criminal behavior. Thus, if captured, combatants must be treated as prisoners of war under the Third Geneva Convention of 1949 rather than as criminals, because as combatants they are legally entitled to fight.

It is up to a State to determine by its own law, however, who is a member of its armed forces. This has particular significance for the determination of when reservists, common in many countries, become members and thus combatants within the meaning of IHL. Once a person is a member of the armed forces of a State it is irrelevant whether that State describes the duties that he/she is to perform as combat or noncombat duties, or whether the members of the armed forces are conscripted or are volunteers. It is also irrelevant whether the State describes those armed forces as special forces, commandos, presidential guards, or by any other name. Where, however, a State incorporates its armed law enforcement agencies (such as its police force) into its armed forces, it must notify the other party to the conflict, for the simple reason that such bodies would not normally be considered to be part of the armed forces of a State, and so not liable to attack as combatants. Certain armed formations in certain states, such as paramilitaries, may or may not be members of the armed forces within the meaning of IHL, depending on how the State’s own law treats such paramilitary forces.

According to the 1977 Additional Protocol I to the Geneva Conventions, States are under an obligation not to recruit child soldiers under the age of fifteen into their armed forces and to take all feasible measures to ensure that children do not take a direct part in hostilities.

The definition of combatants beyond those who fight for the regular armed forces of a State is regulated by IHL.

IHL treats all combatants alike, except for two distinct classifications. One distinction is between officers and other ranks, and is relevant only to certain obligations imposed upon the capturing State in respect to prisoners of war, such as the prohibition against forcing officers to work. The second distinction, between commanders and others, is extremely important since commanders have specific duties placed on them by Additional Protocol I to ensure that their subordinates are aware of their obligations under IHL and to suppress any breaches of these obligations. In addition, commanders are required to prevent any such violation if they have become aware that their subordinates are going to breach IHL. In this way, a commander has command responsibility for the actions of his subordinates, even though he may not directly have ordered the violations.

Captured combatants are entitled to be treated as prisoners of war even if it is alleged that they have committed war crimes. In certain conflicts State leaders have declared that captured air crew are “war criminals” and are not to be treated as prisoners of war. This is contrary to IHL, although a State is entitled and has the right to investigate war crimes, even those alleged to have taken place among POWs. In internal armed conflict, insurgents are not entitled to POW status under the Third Geneva Convention or Additional Protocol I since the conflict is not international. Accordingly, they may be tried for sedition, treason, rebellion, murder, or other crimes under the domestic law of their State; nonetheless, under Article 3 common to the four Geneva Conventions, and notwithstanding that they may be tried by their State, they retain certain minimal protections under IHL, and in particular, may not be summarily executed and must receive the benefit of a regular trial.

(See POW camps; protected persons.)