The cornerstone principle of IHL is that of distinction which all parties to a conflict must abide by at all times, namely to "distinguish between the civilian population and combatants and between civilian objects and military objectives and accordingly [to] direct their operations only against military objectives" (article 48 Additional Protocol I). This means that there must be clear definitional boundaries between the "civilian population" (who are protected persons and may never be deliberately targeted unless they change status to combatants/take up arms, see, e.g., article 50(1) Additional Protocol I), and "combatants" (who may be deliberately targeted). The correct classification is important since, in situations of IAC, under Geneva III combatants are entitled to protection as prisoners of war following capture; and "can be prosecuted only for violations of international humanitarian law, in particular for war crimes" (article 43(2) Additional Protocol I). Though States did not agree to extend such combatants' privileges in NIACs to members of organized armed groups or civilians directly participating in hostilities, they may elect to treat captured fighters as prisoners of war as a matter of policy. (Especially helpful in the drafting of this section was Malzer, 2016, and Pejic, 2012, Ch. 7).
This section gives an overview of the rules governing the classification of combatants (international armed conflicts - IAC) and fighters (non-international armed conflicts - NIAC) and identifies some of the key areas of contention that have surrounded the classification of non-State terrorist actors such as al Qaeda and ISIL.
The starting position is that all members of a belligerent party to a conflict, State or non-State in nature, are combatants. The exception to this general rule are those personnel engaged solely in humanitarian functions (medical and religious personnel) (article 43(2) Additional Protocol I).
Combatants (and therefore also prisoners of war), as defined by IHL, are members of the armed forces of a State or of groups assimilated to a State as is defined by Geneva Convention III (articles 4(A)(1)-(3), and (6)). Notably, article 4(A)(2), in relation to non-regular army combatants, such as those fighting for militias and resistance movements, identifies four key criteria that must be fulfilled in order to fall within the Convention's scope:
(a) That of being commanded by a person responsible for his subordinates.
(b) That of having a fixed distinctive sign recognizable at a distance.
(c) That of carrying arms openly.
(d) That of conducting their operations in accordance with the laws and customs of war.
These original criteria were modified, however, by Additional Protocol I in order to bring non-conventional warfare, such as armed struggles against colonial domination and alien occupation - whom some would consider to be terrorists - within the parameters of the Geneva Conventions (article 1(4)). Though there were some benefits, such as the protection of civilian populations, associated with reflecting the reality of guerrilla warfare, this also led to the relaxing of the original criteria with resultant less clarity as to who constitutes a combatant for the purposes of IHL. Such uncertainties are not assisted by ongoing disagreements regarding whether or not at least some armed groups are engaged in legitimate self-determination struggles or criminal terrorist activities.
Additional Protocol I defines armed forces as comprising "all organized armed forces, groups and units which are under a command responsible to that Party for the conduct of its subordinates" (article 43(1)). Notably, under article 44(3) Additional Protocol I, there was the relaxing of the obligation of combatants to distinguish themselves. These changes have been described in the following terms:
[W]hile, traditionally, belligerents who did not distinguish themselves from the civilian population in a permanent manner lost their right to combatant status, Additional Protocol I now allowed combatants in certain circumstances to distinguish themselves only by carrying arms openly during a military engagement and while they are visible to the enemy in a military deployment preceding an attack.
That said, adverse consequences may arise for individuals who do not fully comply with IHL. For example, they may not be afforded prisoner of war status if captured (see article 46 Additional Protocol I). As with those combatants who comply with all four criteria, those combatants who do not may similarly be criminally prosecuted for violations of IHL.
The travaux preparatoires reveal that such changes were understood and expected by participating delegates to apply only in exceptional circumstances. For example, in contexts where "owing to the nature of hostilities" it was not possible for an armed combatant to distinguish himself except by carrying arms openly during a military engagement or prior to it, namely during wars of national liberation and situations of occupation. There was, however, significant concern among some States, including the US which continues to refuse to ratify Additional Protocol I (and Protocol II), that such modifications risked extending to and protecting "terrorists".
In practice, the significance of such concerns has been minimal in that the obligations, such as to protect civilian populations, under the Geneva Conventions are absolute; acts of violence carried out between recognized combatants are lawful and do not constitute terrorism; the number of national liberation movements or other situations provided for by article 1(4) Additional Protocol I is very small; and most States have become parties to Additional Protocol I, suggesting that they do not agree that the modifications facilitate terrorist acts.
Notably too, direct participation by civilians in hostilities is not in and of itself a war crime (unless carried out perfidiously) since it is an inevitable fact of armed conflict. A person's loss of protection against direct attack (only applicable to civilians not engaged in hostilities) may only be determined by those factors recognized by IHL, namely membership of an armed force which is a belligerent party to a conflict, or a civilian directly participating via a levée en masse or otherwise in the hostilities for the period that they are so engaged. A number of international and domestic sanctions, however, do regulate such conduct. As has been mentioned already, under IHL civilians lose their protected status when actually engaged in direct hostilities, meaning that they can be lawfully targeted and killed by the adversary as for any combatant.
IHL applicable to IACs also permits such civilians to be interned for so long as they are considered to pose a threat to the detaining power, which may be until the end of active hostilities. As, e.g., the ongoing conflict in Afghanistan between the Government and the Taliban demonstrates, this may mean internment for many years if authorized by the United Nations. Furthermore, as with regular armed forces combatants, such civilians may be prosecuted for the commission of war crimes should they attack civilians or civilian objects. In addition, since participating civilians do not enjoy the same combat immunity status as regular armed forces, they may also be criminally prosecuted under domestic law by the detaining State for having taken up arms and committed acts of violence, including against military objectives permitted under IHL, but constituting domestic criminal offences. With such sanctions, the practical and political benefits associated with branding certain acts as "terrorist" in nature are limited other than their related political and ideological connotations.
In contrast to situations of IAC, no such detailed rules exist for NIAC, notably regarding key concepts such as "civilians", "armed forces" and "attacks", nor the regulating of the conduct of military operations in any detail. This is largely due to the concern by many contracting States not to give any impression of legitimacy or privilege to entities taking up arms against them such as dissident armed forces, insurgent groups and other non-State belligerents. That said, Common article 3 to the Geneva Conventions and Additional Protocol II offer some guidance regarding the conduct of hostilities in NIAC situations.
Significantly, the same cornerstone principle of distinction applies equally during NIACs, between "fighters" (rather than "combatants") and between fighters and State forces and civilians. The former category comprises "armed forces", "dissident armed forces" and "other organized armed groups" who are carrying out "sustained and concerted military operations" under "responsible command". The principal purpose of categorizing such persons should relate to their conduct of hostilities and should not affect their treatment if, e.g., captured and deprived of their liberty (see Common article 3(1) to the Geneva Conventions; articles 1(1) and 13(1) Additional Protocol II). Therefore, anyone captured, detained or interned in situations of NIAC may be entitled to the same level of protection under IHL, regardless of their status or involvement in hostilities, and regardless of who detains them, State or non-State parties (Common article 3(1) to the Geneva Conventions; articles 4 and 5 Additional Protocol II), though this remains a highly contested matter including among States.
The other category of "civilians" are members of the "civilian population" and "individual civilians" who "enjoy general protection against the dangers arising from military operations" conducted by these armed forces or groups (Common article 3 to the Geneva Conventions; articles 1(1) and 13(1) Additional Protocol II). Therefore, any direct attacks against this latter category of persons, together with any acts or threats of violence the primary purpose of which is to spread terror among the civilian population, are prohibited (article 13(2) Additional Protocol II).
In situations of NIAC, where no formal privilege of combatancy exists as for IACs, a distinction is made between civilians and those fighting forces of the belligerent parties. It is generally accepted that the effect of Common article 3 and Additional Protocol II is that organized armed groups, as with the armed forces of a State, do not qualify as civilians. Generally, such groups are considered to lose their civilian status and be liable to lawful attack as with combatants in IAC contexts. Consequently, terms such as "fighters", "unlawful" or "unprivileged" combatants or belligerents, are sometimes used to describe such persons.
Such terms, however, have no formal legal status in IHL which does not use them. Significantly, even where such terminology is used, it has no impact on the legal status of or humanitarian protections afforded to such persons under IHL. Technically, the term "unprivileged combatant" means that a person does not have the legal right to participate directly in hostilities (such as a member of the armed forces). Since he does not have combatant privilege, he may be prosecuted for any act or omission provided for under relevant domestic law, even if such conduct is permissible under IHL. In contrast, the activities of a State's armed forces and law enforcement agencies, which comply with IHL, will generally be regarded as permissible and lawful under the national laws of the State concerned.
The term "unlawful combatant" is potentially even more problematic in that though IHL restricts the right to directly engage in hostilities to privileged combatants, it does not prohibit anyone, including civilians, from taking up arms in situations of armed conflicts; it only suspends their protected status during the period of such activity and prohibits certain conduct. In contrast, it is possible for States to adopt legislation that criminalises the conduct of "unprivileged combatancy", therefore making it "unlawful" under their domestic law.
The classification of non-State terrorist actors, such as Al Qaida and ISIL, has been contentious, especially since there is no classification of "terrorist" in IHL, though it does recognize and prohibit terrorist acts. Are they parties to a conflict with the obligations but also privileges associated with IHL? Are they distinguishable from "guerrilla" forces, which fall within the parameters of Additional Protocol I determination of combatants if they meet the required minimum criteria? Or are they civilian criminals who enjoy no such protection (e.g. from prosecution for targeting combatants) and are governed by national and international criminal law? In part, this may depend on whether and to what extent such terrorist groups are connected to a party to a conflict, including in terms of the level of command and control being exercised by and over them. Additionally, even if connected to a party, a further issue to determine is whether or not their activities have any nexus (i.e. connection) to the situation of armed conflict. Do their activities form an integral part of the military activities of a party to the conflict, in which case they may come within the category of combatants (e.g. Al Qaida's direct support of the Taliban in Afghanistan in 2001)? Or does it just so happen that terrorist activities are carried out by a group which is not a party to the conflict but which, e.g., is taking advantage of the weakened position of the State in the territory in which it carries out terrorist activities for its own ideological purposes (in which case they are criminals and should be treated the same as any other terrorist group during peacetime) and which are not linked to or in support of the parties or military objectives of the ongoing conflict.
For such reasons, many controversies and complexities have arisen regarding the classification of terrorist non-State actors who often do not fit comfortably within either of the two categories recognized under IHL governing IAC, namely "combatants" and "civilians". Therefore, descriptive terms (without legal recognition) such as "unlawful" combatants have been used to refer to non-State actors who are engaged in armed activities, but who are not generally combatants as understood by IHL in that they do not normally satisfy the necessary legal criteria as explained above. This category of persons, which is not formally recognized by IHL as previously noted, is different to civilians who may directly participate in hostilities and only lose their protected status whilst so doing, as well as from "unprivileged" members of the armed forces engaged in hostilities on an organized and continuous basis. This is because the acts of terrorist non-State actors do not generally have a sufficiently close or causal relationship with, or, indeed, reach the required threshold of harm in support of a coordinated military operation to achieve a lawful military objective. The criminal acts of non-State terrorist actors are designed instead to take advantage of any weakness of the system of law and order.
These issues are further complicated by the fact that a terrorist may have concurrent classifications, under both criminal justice and IHL approaches. For example, he may be regarded and treated as a terrorist under domestic law in the State he is operating in, but be a member of an organized armed group for the purposes of IHL. Furthermore, it is possible for a person or group to be designated as "combatants" for the purposes of IHL, but to carry out unlawful terrorist activities which IHL prohibits and would generally treat as war crimes (e.g., wilful killing, torture or inhuman treatment, extensive destruction of property not justified by military necessity and carried out unlawfully and wantonly). Similarly, in situations of NIAC, terrorist violence may be perpetrated by any of the entities involved, including the State's armed forces, organized armed groups or civilians participating in hostilities (see Common article 3(1) to the Geneva Conventions and article 6(5) Additional Protocol II).
A specific concern relating to the use of such terms as "unprivileged" or "unlawful" combatant is that they will be misused to afford certain types of combatants or fighters lesser rights and protection than they are entitled to under IHL.
One more important development worthy of note here is that a definition of the crime of aggression was agreed for the text of the Rome Statute of the International Criminal Court in 2010 during the high-level Review Conference. The text of article 8bis defines the crime of aggression as "the planning, preparation, initiation or execution, by a person in a position effectively to exercise control over or to direct the political or military action of a State, of an act of aggression which, by its character, gravity and scale, constitutes a manifest violation of the Charter of the United Nations ". Though reaching international agreement on a definition marked a significant step in terms of the development and codification of international law, due to one of its elements being that only a State may commit a crime of aggression, this international crime is not discussed further in this Teaching Module Series since non-State actors, which are its focus, are not generally considered as falling within the scope of article 8bis (Cohen, 2012, pp. 49-50).
A current phenomenon of growing concern relates to that of 'foreign terrorist fighters' (FTFs), namely the nationals of one State who travel abroad to fight alongside non-State armed groups in the territory of another State. Recently, the key focus has been on the foreign fighters who have joined ISIL in Syria and Iraq, and who are now posing increased threats to their countries of origin as ISIL weakens and fighters return home to continue their violent terrorist activities. Though the exact number of such foreign fighters is unknown, estimates tend to be between 30,000 to 40,000, though not all of these fighters are expected to try to return home. For instance, the Preamble (para. 12) to Security Council Resolution 2178 (2014) identifies these entities as ones of particular concern, though the operational part of the resolution, including the legal framework imposed, is generic.
The international community, both through the United Nations Security Council and nationally, is trying to curb the related threats in a number of ways, including through military methods, detention, prosecution for terrorist offences, travel bans or even the denial of statehood (see Module 3). Though most of the methods being used relate to criminal justice/law enforcement approaches, IHL can play an important role too. As with any other non-State actors, IHL applies where such fighters have a nexus with an ongoing armed conflict, in the same manner as for any other belligerents.
So far as the nationality of a fighter is concerned, this will only have some relevance in IAC situations for determining whether or not a captured fighter is given prisoner of war status by the detaining State (a State may or may not give this protected status to its own captured nationals, there is no consistent State practice on this) or treated as a protected person for the purposes of Geneva Convention IV. Even if a fighter is afforded no protected status, in an IAC context he will be entitled to the minimum protections guaranteed by article 75 Additional Protocol I which is reflective of customary international law. In NIAC situations the nationality of foreign fighters has no significance on their status or how they should be treated if captured; the same rules apply as for any hors de combat fighter, namely Common article 3 and Additional Protocol II in addition to other customary international law norms such as the Martens Clause.