Illustration: Jim Cooke (GMG)

This piece is part of a recurring series that aims to be a complete guide to the laws of war. You can read previous entries here.

The principle of distinction is one of the cornerstones of international humanitarian law (IHL), the laws of armed conflict. IHL does not prohibit the use of violence, and combatants are allowed to target each other in an armed conflict. However, the only legitimate objective of conflict is to weaken the military capacity of the enemy, and the principle of distinction protects civilians who are not participating in the conflict from being made the subject of direct attack.

Advertisement

The principle of distinction consists of two mutually reinforcing elements. First, in the conduct of hostilities, parties to a conflict must distinguish between combatants and the civilian population, and between military objectives and civilian objects. Enemy combatants and military objectives may be made the object of attack, while the civilian population and other protected persons and objects may not be. Individual civilians may only be attacked if and for such time as they directly participate in hostilities. Secondly, combatants are under an obligation to distinguish themselves in their appearance from the civilian population.

The rationale behind this most fundamental of long-standing rules is clear. The interests of military necessity in attacking the enemy is limited by the interests of humanity in not attacking the civilian population and protecting it as far as possible from the effects of conflict. The so-called “civilianization” of conflicts, as more and more conflicts are fought in cities and heavily populated areas, and a larger proportion of conflicts feature civilian participation, presents one of the toughest challenges for international humanitarian law.

Classification Of Persons 

There are two types of armed conflict recognized under international law. International armed conflicts (IACs) are conflicts between two or more nations, situations of military occupation, or qualifying wars of national liberation. Non-international armed conflicts (NIACs) are qualifying conflicts between a state and a non-state armed group, or between multiple non-state armed groups. To take two examples from this century, the United States’ conflict with Iraq constituted an IAC, while its conflict with the Islamic State constituted a NIAC. (Situations of violence which do not satisfy the criteria necessary to constitute a NIAC are governed by regular domestic law enforcement and not international humanitarian law.)

Advertisement

In either type of conflict, parties must distinguish between enemy combatants and civilians. For the purposes of the principle of distinction, every person must either be a member of a party to the conflict, or is otherwise a civilian.

There is one exception to this neat categorization, and it applies to IAC only. There can be an additional (somewhat anomalous) category of participants known as levée en masse (French for “mass uprising”), which describes inhabitants of a non-occupied territory who, on the approach of the enemy, spontaneously take up arms to resist the invading forces without having had time to form themselves into regular armed units, provided they carry arms openly and respect the laws and customs of war. This is the only category of persons who lose their civilian status by their conduct rather than by membership of a group, and it does not have wide application in modern warfare.

In each type of conflict, we therefore have a universe of three mutually exclusive categories for the purposes of the principle of distinction:

  • In IAC, every person must be either: (i) a member of armed forces of a party to the conflict; (ii) a participant in a levĂ©e en masse; or (iii) a civilian.
  • In NIAC, every person must be either: (i) a member of armed forces of a state party to the conflict; (ii) a member of an organized armed group of a (non-state) party to the conflict; or (iii) a civilian.

Advertisement

A person’s classification may change according to the armed conflict in question. Members of Argentinian and UK armed forces were classified as members of armed forces of a party to the conflict during the Falklands War of 1982, but would simultaneously have been considered civilians for the purposes of the 1977-1992 Mozambican Civil War, to which their nations were not parties. In situations where several different parties are simultaneously fighting numerous overlapping conflicts on the same territory, a person may simultaneously be a member of a party to one conflict but be considered a civilian in relation to another conflict, all in the same warzone. This strange-sounding result nevertheless makes conceptual sense—that person is targetable by the enemy in the conflict his or her party is fighting, but is generally not targetable by the parties in any conflicts it is not fighting.

For classification purposes, the above analysis is unaffected by the fact that a person or group may be designated as terrorists, pirates, gangsters, hostage-takers, or any similarly undesirable label. Of course, acts of terrorism are prohibited under IHL and are criminalized (whether in the context of an armed conflict or not) by various international treaties, and piracy is one of the oldest crimes in international law. However, these labels (whether accurate or not) are irrelevant to a person’s or group’s classification under IHL—all that matters is whether an armed conflict exists as defined under international law, and then which one of the above categories a person falls into according to whether they are a member of a party to that conflict or not.

For the purposes of the principle of distinction, members of groups who participate in a conflict—members of state armed forces, members of non-state armed groups, and participants in levées en masse—may be collectively referred to as combatants, giving us the division between combatants and civilians. Be careful with this terminology, though, as the word is also used elsewhere in IHL—the use of the word “combatant” in this context does not necessarily imply combatant privilege (which we discuss below), while in IAC the definition of combatant (members of the armed forces of a party to the conflict other than medical and religious personnel) is the starting point for who is entitled to prisoner of war status.

Advertisement

Note that the above categorization trichotomies apply for the purposes of the principle of distinction only. There are different categorizations in IHL for other purposes, such as for determining protected status when a person is in the power of the enemy (which we will explore in a future entry in this series).

Consequences Of Classification 

There are several important consequences resulting from a person’s classification for the purposes of the principle of distinction.

Advertisement

Members of armed forces to international armed conflicts enjoy combatant privilege: the right to directly participate in hostilities. This includes an immunity from being prosecuted for using force against persons or objects in a manner which is consistent with international humanitarian law, such as the lawful killing or wounding of an enemy combatant, which would ordinarily be a violation of domestic law in peacetime. They nevertheless are obliged to respect IHL and may be prosecuted for violations of it that they may commit. Combatant privilege—which applies even if members of armed forces have been sent to fight an illegal war under the independent rules governing the use of force—is one of the oldest rules in all of international law, as states would never accept their forces being subject to prosecution merely for fighting on their country’s behalf. Participants in levées en masse also enjoy combatant privilege.

Combatant privilege is not extended to members of non-state parties to a NIAC or to civilians. IHL itself does not privilege nor prohibit their participation in hostilities—the absence of the right to do so does not imply a prohibition at IHL. Any such prohibition must come from another source—most commonly, the domestic law of most countries itself criminalizes the taking up of arms against the territorial state. Therefore, a civilian or a member of a non-state organized armed group who conducts an attack during a NIAC which is proportionate and directed at military objectives would not breach the rules of international humanitarian law, but may have breached domestic laws such as those against treason or murder. It is a rule of customary international law—a dense body of unwritten law binding on all nations in recognition of “a general practice accepted as law”—that at the end of hostilities in a NIAC, “the authorities in power” (whoever that ends up being) must endeavour to grant the broadest possible amnesty to persons who have participated the conflict, or those deprived of their liberty for reasons related to the armed conflict, with the exception of persons suspected of, accused of, or sentenced for war crimes.

During the conduct of hostilities in an armed conflict, combatants are targetable simply by virtue of their membership of their group—they may be lawfully targeted at all times until they are rendered hors de combat (French for “outside the fight”), being anyone who is in the power of an adverse party, is defenseless (because of unconsciousness, shipwreck, wounds or sickness), or who expresses an intention to surrender, and abstains from any acts of hostility and does not attempt to escape.

Advertisement

By contrast, civilians may only be targeted if and for such time as they directly participate in hostilities—a concept discussed further below. The principle of distinction therefore operates to protect the civilian population generally, but not necessarily to protect all civilians at all times, as they may be rendered targetable by their conduct even if they are not a member of a party to a conflict.

Under the statute of the International Criminal Court, “intentionally directing attacks against the civilian population as such or against individual civilians not taking direct part in hostilities” constitutes a war crime in both IAC and NIAC. The prohibition on directing attacks at civilians is also found in other international instruments such as the Convention on Certain Conventional Weapons Protocols II and III, the Ottawa Convention prohibiting anti-personnel landmines, and in the military manuals of many nations of the world, including that of the United States.

The rule that attacks must not be directed at the civilian population does not prohibit all civilian casualties in armed conflict. As we will see in a future entry in this series, in the conduct of hostilities, an attack which targets military objectives but results in incidental loss of civilian life, injury to civilians,or damage to civilian objects may be lawful if such loss “is not excessive in relation to the concrete and direct military advantage anticipated”.

Advertisement

Direct Participation In Hostilities 

What acts constitute “direct participation in hostilities” which cause civilians to lose their protection from attack under IHL? The notion is not expressly defined in international law. It’s a hugely important question, as the loss of protection can have deadly consequences and should not be imputed lightly. In 2009, the International Committee of the Red Cross (ICRC) released an interpretive guidance which provided recommendations reflecting its interpretation of the notion of direct participation in hostilities.

According to the ICRC, a specific act constitutes direct participation in hostilities if it satisfies each of the following three (separate but related) criteria:

  • The act must reach the required threshold of harm. If an act is likely to adversely affect the military operations or military capacity of a party to the conflict, the threshold is very low and almost any act will reach it—killing or wounding members of the party, guarding its captured personnel, clearing landmines that it had placed, or transmitting tactical targeting information for an attack. Alternatively, acts which are likely to inflict death, injury, or destruction on persons or objects protected against direct attack—such as attacks directed against civilians and civilian objects—also meet the threshold.
  • There must be direct causation between the act and the harm likely to result either from that act, or from a coordinated military operation of which that act constitutes an integral part. At a high level, a distinction can be drawn between (on the one hand) the conduct of hostilities and (on the other) the general war effort and so-called war-sustaining activities. For a specific act to qualify as “direct” rather than “indirect” participation in hostilities, the harm in question must be brought about in one causal step. Indirect causation of harm—and therefore not acts which constitute direct participation in hostilities—could come about by imposing sanctions on a party to an armed conflict, participating in scientific research and design of weapons, delivering or preparing food for members of armed forces, or recruiting and training personnel. By contrast, direct causation of harm could come about by serving as a lookout in an ambush, by operating an unmanned aerial vehicle by remote control (even from halfway across the world), by driving an ammunition truck to an active firing position at the front line (though not by driving the ammunition to a port for shipping to a conflict zone), or instructing troops in the execution of a specific military operation.
  • The act must satisfy the belligerent nexus by being specifically designed to directly cause the required threshold of harm in support of a party to the conflict and to the detriment of another. Acts not satisfying this criterion might include “regular” violent crime committed for reasons unrelated to the conflict, acts of individual self-defense, the stealing of military equipment for private use, or the unintentional blocking of a strategically important area by large groups of refugees or other fleeing civilians.

Advertisement

Civilians enjoy protection against direct attack in each type of armed conflict “unless and for such time” as they take a direct part in hostilities. This rule gives rise to the so-called “revolving door” of protection whereby the archetypal civilian “farmer by day, fighter by night”—a person residing in a warzone who carries out tasks which aid a party to a conflict while not being a member of that party—may repeatedly lose and regain protected status during a conflict. By the same token, workers of private military and security companies—an increasingly large industry who contract to perform a variety of functions for armed forces during a conflict—are civilians under IHL and are often found to directly participate in hostilities. Typically, contractors’ terms of engagement would state that they are not being drafted to perform functions that would constitute direct participation, but they may nevertheless on the ground do so—when providing security for the transport of military personnel or equipment, for example.

According to the ICRC, the notion of direct participation in hostilities is important in determining which persons are to be considered members of an organized armed group of a non-state party to a conflict. Determining whether or not a person is a member of a nation’s armed forces is usually straightforward, as they will ordinarily have undergone formal training and been issued with a rank and identification number. However, determining membership of a non-state armed group is usually more difficult, as membership in such irregularly constituted groups will have no basis in domestic law and may not be formalized through any recorded act of integration (except in the case of dissident armed forces—state armed forces that have turned against the government). Because IHL refers to the concept of organized armed groups in a strictly functional sense, the ICRC says that the decisive criterion is therefore whether a person assumes a continuous combat function involving his or her direct participation in hostilities, such that their function corresponds to that collectively exercised by the group as a whole, namely the conduct of hostilities.

Feasible precautions must be taken in determining whether a person is a civilian or whether a civilian is directly participating in hostilities. A presumption of protection must be applied in the case of doubt.

Advertisement

Obligation Of Combatants To Distinguish Themselves 

This rule is fundamental for the protection of the civilian population—belligerents must be able to tell the difference between combatants and civilians in order to protect the latter from the effects of conflict as far as possible.

The rule seeks to ensure that protected and unprotected categories are distinct from one another, not necessarily distinct in the abstract. Combatants do not need to wear bright flashing neon lights to draw attention to themselves, nor to wave their party’s flag as they conduct their operations. The use of camouflage is consistent with the obligation to distinguish, because foliage is not a protected category and civilians generally do not wear camouflage. Similarly, a combatant would not violate the obligation to distinguish by dressing as a polar bear, because polar bears are not protected under IHL. (In a similar vein, ruses of war, such as the use of decoys, mock operations, and misinformation are likewise not prohibited in the conduct of hostilities, because they do not involve placing the civilian population at risk.)

Advertisement

The 1977 First Additional Protocol to the Geneva Conventions contains a provision which recognizes that “there are situations in armed conflicts where, owing to the nature of the hostilities an armed combatant cannot so distinguish” him or herself. In such situations he or she retains combatant status, provided that they carry arms openly during each military engagement and during such time as they are visible to the adversary while is engaged in a military deployment preceding the launching of an attack. This provision is not a rule of customary international law and therefore only applies to IACs within or between the 174 states parties to the First Additional Protocol.

Failure to comply with the obligation to distinguish can have serious consequences. In IAC, individual combatants who do not distinguish themselves from the civilian population while they engaged in an attack or in a military operation preparatory to an attack forfeit their right to prisoner of war status. Individual combatants captured while engaging in espionage likewise do not have the right to prisoner of war status. If a party to a conflict as a whole does not distinguish itself, it may be that all of its members are denied prisoner of war status. A combatant who participates in hostilities while not distinguishing themselves may be convicted under domestic law—as has happened in cases varying from German soldiers captured in plain clothes in New York during World War II, to members of Egyptian armed forces who infiltrated Israeli territory and launched attacks in civilian attire, to a Nigerian rebel soldier carrying out a mission in disguise during the Biafran War, and non-distinguished Indonesian personnel who carried out a lethal explosion in Singapore during the Malaysia-Indonesia armed conflict.

The next installment of this series will cover the protection of the wounded, sick, and shipwrecked.