The Practical Guide to Humanitarian Law

« Calling things by the wrong name adds to the affliction of the world. » Albert Camus.

International Armed Conflict (IAC)

Armed conflicts are both a state of fact and a question of law. Since 1945, the United Nations prohibits the recourse to armed force in the relations between States, except in cases of self-defense or aggression. Nonetheless, the definition of aggression as a crime under international criminal law was adopted only in 2010. Besides, there is no international legal definition of armed conflicts as such. Since 1949, Common Article 2 to the four Geneva Conventions gives a definition of international armed conflict that triggers the application of humanitarian law. Common Article 3 to the four Geneva Conventions provides the minimum rules applicable in non-international armed conflicts, without giving a clear definition of such conflict. The first 1977 Additional Protocol to the Geneva Conventions as well as the jurisprudence of international tribunals have broadened the definition of international armed conflicts and have provided criteria of interpretation of this definition. The issue entailed in those definitions lies in the obligation to respect rules of conventional and customary humanitarian law specifically applicable to international armed conflicts, rather than the more restricted rules applicable to non-international armed conflicts.

Conventional Definition: Armed Conflict between States

According to conventional international humanitarian law, this term describes armed conflicts between two or more States, cases of military occupation of all or part of the territory of a High Contracting Party, as well as wars of national liberation (GCI–IV Common Art. 2, API Art. 1.3–4).

The definition of Common Article 2 covers cases of declared wars as well as any armed conflict where the state of war has not been recognized. Since 1949, the application of international humanitarian law is no longer dependent on the formalism of a war declaration, or the recognition of the state of belligerency by one of the concerned States. This definition is based on objective criteria intended to avoid the political polemics on qualification.

The law applicable to international armed conflicts also covers all cases of partial or total occupation of the territory of a High Contracting Party, even if the said occupation meets with no armed resistance and there are therefore no armed clashes, or if those armed clashed are with non-state armed groups on the territory of the occupied State.

The first Additional Protocol of 1977 considers that wars of national liberation in which a population is fighting against colonial domination, foreign occupation, or racist regimes are international armed conflicts. In general, this is also the case for wars resulting from people’s attempts to exercise their right to self-determination (API Art. 1). The law of international armed conflicts can therefore apply to this type of conflict on the condition that the authority representing the people involved in the conflict formally agrees to implement the Geneva Conventions and its first Additional Protocol (API Art. 96.3).

Conventional and customary international humanitarian law do not give a clear definition of the notion of armed conflict. The commentary on Common Article 2 specifies that any difference arising between two States and leading to the intervention of members of the armed forces is an armed conflict within the meaning of the Geneva Conventions, even if one of the parties denies the existence of a state of war. The commentary states that the duration of the conflict, the number of deaths, or the number of military forces involved makes no difference on the qualification of the conflict. The simple fact that the armed forces of one of the parties have captured members of the adverse armed forces, even if there have been no dead, is sufficient to activate the law applicable to international armed conflicts. Therefore, the existence of an international armed conflict does not depend on any requirement regarding the threshold of violence and the intensity of the armed clashes, contrary to the rules applicable to internal armed conflicts.

Jurisprudential Definition: International Armed Conflicts or “Internationalized” Armed Conflicts

The complexity of contemporary armed conflicts involving a wide range of actors, from State to non-state actors and international armed forces, sometimes spilling over to the territory of States not officially parties to the conflict, raises questions of qualification and of law applicable to these actors and situations.

While the direct military involvement of several States is easy to establish, it doesn’t account for the reality of most contemporary armed conflicts, which defy formal legal criteria. Indeed, some armed conflicts can occur on the territory of several States without directly involving their national armies. Others occur on one national territory but involve non-state armed groups, operating from the territory of a neighboring State, with or without the control of the latter. Finally, some armed conflicts occur outside the national territory of one party to the conflict. It is also necessary to go beyond legal appearances concerning the non-state nature of an armed actor and to verify if it actually acts on behalf or under the control of another State.

Finally, the presence of international armed forces, under UN mandate or not, can also modify the nature of an armed conflict if their mandate includes the direct participation in combat and does not limit the recourse to force to self-defense.

International jurisprudence has defined the criteria of internationalization of an armed conflict that does not directly oppose two or more States and which is not international in the literal sense of the definition.

Support and Control of Nonstate Armed Groups

Several decisions of the International Court of Justice and International Criminal Tribunals have examined the conditions under which the acts of non-state armed groups could be attributed to a third State, and as such be qualified as an international conflict, or an “internationalized” armed conflict. In its judgment of 15 July 1999 in the Tadic Case , the International Criminal Tribunal for the Former Yugoslavia gave its opinion of the qualification of conflict. The Tribunal affirmed that “an internal armed conflict breaking out on the territory of a State . . . may become international (or, depending upon the circumstances, be international in character alongside an internal armed conflict) if (i) another State intervenes in that conflict through its troops, or alternatively if (ii) some of the participants in the internal armed conflict act on behalf of that other State” (ICTY, IT-94-1-A, para. 84).

International Criminal Tribunals have attempted to specify the notions of direct support and control, which could engage the responsibility of a State for actions of a non-state armed group or to qualify this group as a State agent. There is general consensus on the fact that for a conflict to be internationalized, the control of an armed group by another State has to go beyond mere material support. In its judgment in the Tadic Case , the International Criminal Tribunal for the Former Yugoslavia (ICTY) specified that in order to hold a State liable for the acts of an armed group, it must be proved that this State wields overall control over the group, not only by equipping and financing it but also by coordinating or helping in the general planning of its military activity. Nonetheless, it would not be necessary to prove that the State is directly involved in the decisions concerning each specific military action. This theory of the overall control and the criteria that are associated to it has been developed in the international criminal tribunals’ decisions (infra Jurisprudence).

Nevertheless, there is a controversy between the International Court of Justice and the International Criminal Tribunals with regard to the level of control required to consider that an armed group acts in fact on behalf of another State, a level that would hold the State liable for actions by the armed group. Instead of the “overall control” defined by the International Criminal Tribunals, the ICJ requires an “effective control,” which is much more restrictive and implies a lack of autonomy of the armed group vis-à-vis the State concerned. The ICJ tried to reconcile these two notions by considering in a 2007 decision that proving the existence of the overall control would be sufficient to qualify a situation of international armed conflict. However, the Court stated that this control had to be practically total if it was about holding the State liable for the criminal acts perpetrated by the foreign armed group (infra Jurisprudence).

The ICJ recalled in a very useful way that humanitarian law should be interpreted more broadly than through the lens of international law of State responsibility of international criminal law. The contribution of international criminal jurisprudence in the field of humanitarian law should be studied carefully in the light of the difference of the objectives pursued by those different branches of international law. ▸ International Court of JusticeResponsibility

Presence of International Armed Forces Authorized by the UN

Concerning peacekeeping operations and other international armed interventions authorized by the United Nations, there have been numerous legal debates on their status, if they should be considered as parties to the conflict or mediators. These debates have influenced the qualification of the conflicts in which they are deployed and the nature of the humanitarian law applicable to their members. It is now admitted that the sole presence of multinational forces deployed under UN mandate in an armed conflict is not sufficient to internationalize the conflict. Indeed, in the majority of situations, those international armed forces are deployed with the consent of the concerned States and are not authorized to use force outside self-defense. As such, they cannot be considered as parties to the conflict. The Rome Statute of the International Criminal Court has recognized the civilian status of these forces in certain situations, by envisaging that the deliberate attack on these personnel constitutes a war crime. Nonetheless, in cases where international forces are authorized to use force in an offensive way and to participate in actions of combat, they lose this civilian status. The conflict can then be considered internationalized, and those forces have to respect relevant provisions of international humanitarian law. ▸ Peacekeeping

International Humanitarian Law Applicable to International Armed Conflicts

The rules applicable to international armed conflicts are the four 1949 Geneva Conventions and the 1977 Additional Protocol I, as well as rules of customary international humanitarian law.

The rules of humanitarian law were developed mainly in the context of international armed conflicts. Today, the regulations for these conflicts are still the most detailed, establishing limitations on the means and methods of warfare and imposing obligations on the parties to the conflict in terms of relief and protection of civilian populations and persons hors de combat . They regulate the rights of humanitarian organizations and the punishment of war crimes.

International jurisprudence has also affirmed that the rules applicable to international armed conflicts could be used to interpret or complement the ones applicable to internal armed conflicts.

In addition to the mandatory application in cases covered by the Conventions (conventional application), some of IHL and customary IHL rules can be implemented on an ad hoc basis by way of special agreement and with the consent of the parties to the conflict. ▸ Special agreement

The decisions of International Criminal Tribunals have defined criteria that allow a better apprehension of the reality of armed conflicts. But those decisions have also opened spaces for technical and practical debates that are not compatible with the requirements of immediate application of humanitarian law in conflict. Indeed, it is neither possible nor desirable to defer the qualification of a conflict and therefore the determination of the law applicable to it by waiting for the decision of a judge who has to rule after the facts on the different elements and criteria of the specific case. This is why the spirit of humanitarian law was to limit its own definition of armed conflicts, both international and non-international, to simple and objective criteria that could apply automatically to all situations. Humanitarian law also provides that all parties to the conflict commit to implement all or part of the Conventions at the beginning of the hostilities by way of special agreement, in case the immediate conventional application would be problematic.

Those decisions have fueled legal debates on questions linked to international criminal law and State responsibility. They did not clarify the content of humanitarian law applicable in this kind of conflict, notably in terms of assistance and protection or concerning the status of the members of non-state armed groups.

The current tendency is to secure the immediate application of humanitarian law by recognizing the mixed character of some armed conflicts, which can have international and non-international elements simultaneously. In such situations, humanitarian law could apply at a minimum and differentially depending on the nature of the armed actors. It would allow the armed clashes between governmental forces and international forces to be subjected to the law applicable to international armed conflicts. The other types of armed clashes that oppose several non-state armed groups or which oppose them to governmental forces or international forces should at a minimum be covered by the law applicable to non-international armed conflicts.

This fragmented approach leads to the application of different legal regimes on the same territory depending on the nature of the opposing parties. This approach takes into account the possible coexistence of several types of conflicts occurring simultaneously on the same territory and involving State and non-state actors which have different capacities as well as different obligations with regard to national law and international law, notably concerning law enforcement, prosecution, and detention.

The heaviness of this system is partially compensated for by the recent unification of rules of customary international humanitarian law, applicable to both international and non-international armed conflicts. The unification and expansion of the definitions of crimes applicable to international and non-international armed conflicts by the Rome Statute of the International Criminal Court has also put things into perspective.

Finally, this legal uncertainty could be compensated by parties to the conflict through the application—in case of doubt—of the most protective provisions of humanitarian law. This would mitigate the multiplication of legal regimes applicable to armed conflicts and prevent governments from creating new categories of conflict that would escape from any application of humanitarian law. On this particular issue, the U.S. Supreme Court recalled that the war on terrorism did not constitute a third category of armed conflict. In the Hamdam Case (U.S. Supreme Court, no. 05-184, Salim Ahmed Hamdam, petitioner, v. Donald H. Rumsfeld, Secretary of Defense et al., on writ of certiorari to the U.S. Court of Appeals for the District of Columbia circuit , June 26, 2006, pp. 65–69), the U.S. Supreme Court rejected the abusive interpretation of conflict qualification criteria used by U.S. authorities to invoke the existence of a third category of armed conflict not covered by existing humanitarian law.

Non-international armed conflictTerrorism


  1. The Control of Non-state Armed Groups in the International Criminal Tribunals’ Jurisprudence

In the Tadic Case of 15 July 1999 (IT-94-1-A), the ICTY Appeals Chamber consolidated the legal argumentation concerning the control of non-state armed groups by third States.

  • Concerning the attribution of the acts of an armed group to a State, the appeals Chamber stated that the State must exercise an overall control over that group (para. 131):

In order to attribute the acts of a military or paramilitary group to a State, it must be proved that the State wields overall control over the group, not only by equipping and financing the group, but also by coordinating or helping in the general planning of its military activity. Only then can the State be held internationally accountable for any misconduct of the group. However, it is not necessary that, in addition, the State should also issue, either to the head or to members of the group, instructions for the commission of specific acts contrary to international law.

  • Concerning the constitutive elements of the overall control exercised by the State, some elements are less strict for an organized armed group than for individuals or unorganized groups (para. 137):

international rules do not always require the same degree of control over armed groups or private individuals for the purpose of determining whether an individual not having the status of a State official under internal legislation can be regarded as a de facto organ of the State.

° With regard to organized armed groups, the overall control must go beyond the mere provision of financial assistance or military equipment or training (para. 131 supra and 137):By contrast, control by a State over subordinate armed forces or militias or paramilitary units may be of an overall character (and must comprise more than the mere provision of financial assistance or military equipment or training). This requirement, however, does not go so far as to include the issuing of specific orders by the State, or its direction of each individual operation. Under international law it is by no means necessary that the controlling authorities should plan all the operations of the units dependent on them, choose their targets, or give specific instructions concerning the conduct of military operations and any alleged violations of international humanitarian law. The control required by international law may be deemed to exist when a State (or, in the context of an armed conflict, the Party to the conflict) has a role in organising, coordinating or planning the military actions of the military group, in addition to financing, training and equipping or providing operational support to that group. Acts performed by the group or members thereof may be regarded as acts of de facto State organs regardless of any specific instruction by the controlling State concerning the commission of each of those acts.

° Concerning individuals or groups that are not militarily organized, the State responsibility can be triggered only if it is established that it gave specific orders to this group or to these individuals to commit the acts they are accused of (para. 137):Where the question at issue is whether a single private individual or a group that is not militarily organised has acted as a de facto State organ when performing a specific act, it is necessary to ascertain whether specific instructions concerning the commission of that particular act had been issued by that State to the individual or group in question; alternatively, it must be established whether the unlawful act had been publicly endorsed or approved ex post facto by the State at issue.

This definition of overall control has been confirmed by the ICTY appeals Chamber in subsequent cases. It specified that “the ‘overall control’ test calls for an assessment of all the elements of control taken as a whole, and a determination to be made on that basis as to whether there was the required degree of control” ( Aleksovski Case , ICTY Appeals Camber, 24 March 2000, para. 145). In the Čelebići Camp Case ( Mucić et al .) of 20 February 2001, the ICTY Appeals Chamber validated the legal reasoning of overall control and its relevance, which frees it from the legal formalism and triggers State responsibility for activities of supposedly independent groups who act in fact on behalf of this State or in its interest. The tribunal also specified that when

the controlling State in question is an adjacent State with territorial ambitions on the State where the conflict is taking place . . . the ‘overall control’ test could . . . be fulfilled even if the armed forces acting on behalf of the ‘controlling State’ had autonomous choices of means and tactics although participating in a common strategy along with the ‘controlling State’ (para. 47).

The criterion of “overall control” defined by the ICTY is less strict that the one of “effective control” subsequently used by the International Court of Justice.

  1. The Control of Non-state Armed Groups in the Jurisprudence of the International Court of Justice

In its judgment of 27 June 1986, relative to the Military and Paramilitary Activities in and against Nicaragua (Nicaragua v. United States of America), Merits, Judgment, I.C.J. Reports 1986, p. 14, the ICJ held that

even if preponderant or decisive, in the financing, organizing, training, supplying and equipping of the contras , the selection of its military or paramilitary targets, and the planning of the whole of its operation, is still insufficient in itself, on the basis of the evidence in the possession of the Court, for the purpose of attributing to the United States the acts committed by the contras . . . . For this conduct to give rise to legal responsibility of the United States, it would in principle have to be proved that that State had effective control of the military or paramilitary operations in the course of which the alleged violations were committed. (para. 115)

In its judgment of 26 February 2007, concerning the Application of the Convention on the Prevention and Punishment of the Crime of Genocide (Bosnia and Herzegovina v. Serbia and Montenegro , Judgment, ICJ Reports 2007, p. 43), the ICJ restated the difference between the notions of “overall control” and “effective control.” The Court implicitly recognized that the “overall control” criterion was relevant for the qualification of an international armed conflict, but it clearly stated that it was insufficient to trigger State responsibility for the unlawful acts perpetrated by armed groups. In doing so, the Court did a differentiated interpretation of humanitarian law on the one hand and of criminal law or of the law of international responsibility of States on the other hand. “Insofar as the ‘overall control’ test is employed to determine whether or not an armed conflict is international, which was the sole question which the Appeals Chamber (ICTY in the Tadic Case ) was called upon to decide, it may well be that the test is applicable and suitable” (para. 404). On the contrary,

State’s responsibility can be incurred for acts committed by persons or groups of persons—neither State organs nor to be equated with such organs—only if, assuming those acts to be internationally wrongful, . . . are attributable to it. . . . This is so where an organ of the State gave the instructions or provided the direction pursuant to which the perpetrators of the wrongful act acted or where it exercised effective control over the action during which the wrong was committed. In this regard the “overall control” test is unsuitable, for it stretches too far, almost to breaking point, the connection which must exist between the conduct of a State’s organs and its international responsibility. (para. 406)

In this case, the ICJ recalled that

it is appropriate to look beyond legal status alone, in order to grasp the reality of the relationship between the person taking action, and the State to which he is so closely attached as to appear to be nothing more than its agent: any other solution would allow States to escape their international responsibility by choosing to act through persons or entities whose supposed independence would be purely fictitious (para. 392).

But the Court specified that in order to trigger the State responsibility, it has to be demonstrated that

  1. the persons who performed the acts alleged to have violated international law were in general in a relationship of ‘complete dependence’ on the respondent State and that ii) they acted in accordance with that State’s instructions or under its ‘effective control’ (para. 400).

The Court added that it must be shown that

this ‘effective control’ was exercised, or that the State’s instructions were given, in respect of each operation in which the alleged violations occurred, not generally in respect of the overall actions taken by the persons or groups of persons having committed the violations (para. 400).

  1. Situations of Military Occupation

Concerning the law applicable to confrontations linked to situations of military occupation, the Israel Supreme Court acknowledged in its judgment of 11 December 2005 that the conflict between Israel and the armed groups present in the region, whether they are considered as terrorist organizations or not, is considered an international armed conflict ( Public Committee against Torture in Israel , HCJ 769/02, para. 18).

In several decisions, the International Court of Justice has confirmed the application of humanitarian law to situations of occupation.

Customary international lawGeneva Conventions of 1949 and Additional Protocols I and II of 1977Internal disturbances and tensionsInternational Humanitarian LawLegal status of the parties to the conflictNon-international armed conflictNon-state armed groupsOccupied territoryParties to the conflictPeacekeepingSituations and persons not expressly covered by humanitarian lawSpecial agreement

For Additional Information: Bartels, Roger. “Timelines, Borderlines and Conflicts: The Historical Evolution of the Legal Divide between International and Non-international Armed Conflicts.” International Review of the Red Cross 873 (March 2009): 35–67.

Carswell, A. J. “Classifying the Conflict: A Soldier’s Dilemma.” International Review of the Red Cross 873 (March 2009): 143–61.

Corn, G. S. “Hamdan, Lebanon, and the Regulation of Armed Hostilities: The Need to Recognize a Hybrid Category of Armed Conflict.” Vanderbilt Journal of Transnational Law 40, no. 2 (March 2007): 295–355.

Crawford, Emily. “Unequal before the Law: The Case for the Elimination of the Distinction between International and Non-international Armed Conflict.” Leiden Journal of International Law 20, no. 2 (2007): 441–65.

Paulus, A., and M. Vashakmadze. “Asymmetrical War and the Notion of Armed Conflict—a Tentative Conceptualization.” International Review of the Red Cross 873 (March 2009): 95–125.

Pejic, Jelena. “Status of Armed Conflicts.” In Perspectives on the ICRC Study on Customary International Humanitarian Law , edited by Elisabeth Wilmshurst and Susan Breau, 77–100. Cambridge: Cambridge University Press, 2007.

Schondorf, R. S. “Extra-State Armed Conflicts: Is There a Need for a New Legal Regime?” New York University Journal of International Law and Politics 37, no. 1 (2004): 61–75.

Sivakumaran, Sandesh. “Re-envisaging the International Law of Internal Armed Conflict.” European Journal of International Law 22, no. 1 (2011): 219–64.

Stewart, James. “Towards a Single Definition of Armed Conflict in International Humanitarian Law: A Critique of Internationalized Armed Conflict.” International Review of the Red Cross 850 (June 2003): 313–50.

“Typology of Armed Conflicts.” International Review of the Red Cross 873 (March 2009).

Vité, Sylvain. “Typology of Armed Conflicts in International Humanitarian Law: Legal Concepts and Actual Situations.” International Review of the Red Cross 873 (March 2009): 69–94.

Willmott, Deirdre. “Removing the Distinction between International and Non-international Armed Conflict in the Rome Statute of the International Criminal Court.” Melbourne Journal of International Law 5, no. 1 (2004): 196–219.

Article also referenced in the 4 following categories :