Author: Mitt Regan

1  Basis for the Claim of Armed Conflict

2  Where is the Battlefield?

3  Which Groups are the Enemy?

4  Who are Combatants?

5  State Consent

6  Detention

7  Conclusion

A distinctive element of United States (US) counterterrorism strategy is its reliance on military force in addition to various law enforcement measures.  The US regards itself as being engaged in an armed conflict with Al Qaeda and the Taliban since 2001, with the Islamic State since 2004 (originally in the form of Al Qaeda in Iraq), and with Al-Shabaab since 2016.  Most of the operations under the US targeted killing program are conducted under this legal authority, while a smaller percentage are conducted as self-defense operations outside of armed conflict.

The significance of designating actions against members of these four groups as part of an armed conflict is that it triggers the application of standards for the use of force under International Humanitarian Law (IHL) set forth in the Geneva Conventions and their two Additional Protocols.  These standards are more permissive than those under a law enforcement framework. Most notably, they provide that: (1) any person designated as a combatant in an armed conflict may be targeted with lethal force at any time by virtue of their status as a combatant, regardless of their conduct at the moment and (2) attacks on military targets may permissibly cause foreseeable but unintentional harm to civilians and civilian property as long as such harms are not “excessive” compared to the military advantage gained from the attack.

1  Basis for the Claim of Armed Conflict

The US position is that the attacks of 11 September 2001 were not simply crimes, but acts of war. International law provides that a state may be involved in what is known as a non-international armed conflict (NIAC) with a non-state group when there is (1) fighting of a certain level of intensity (2) with non-state actors that are organized in a sufficiently integrated way. The US maintains that the almost 3,000 deaths from the attacks, along with the widespread destruction of property that occurred, were on a scale that satisfies the requirement that violence be of a sufficient level of intensity. It points to the level of coordination necessary to plan the attacks from abroad, as well as prior Al Qaeda attacks on US property and persons in 1993 (the World Trade Center), 1998 (US embassies in Kenya and Tanzania), and 2000 (the USS Cole), as indicative of Al Qaeda’s capacity to function as an organized group rather than as a diffuse set of terrorists. Based on these factors, the US maintains that the 11 September attacks were simply one attack in an ongoing Al Qaeda campaign against the US that constitutes an armed conflict.

Accordingly, the US Congress passed the Authorization for the Use of Military Force (AUMF) on 18 September 2001, which authorized the President to “to use all necessary and appropriate force against those nations, organizations, or persons he determines planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001, or harbored such organizations or persons, in order to prevent any future acts of international terrorism against the United States by such nations, organizations or persons.”

The US invaded Afghanistan in October 2001 with the claim that it was conducting an operation in self-defense against Al Qaeda and its Taliban host state in the course of this armed conflict.  This position was widely supported in the international community.  More controversially, the US contends that it continues to be engaged in an armed conflict with Al Qaeda and its allies in various locations even after the fall of the Taliban. As the Legal Adviser for the US State Department argued in 2007:

The United States was and continues to be in an armed conflict with al Qaida, one that is conceptually and legally distinct from the conflict with the Taliban in Afghanistan. It cannot reasonably be argued that the conflict with al Qaida ended with the closure of al Qaida training camps and the assumption of power by a new government in Afghanistan. Al Qaida’s operations against the United States and its allies continue not only in and around Afghanistan but also in other parts of the world.

The State Department Legal Adviser in the Obama administration echoed this view in 2010:

As recent events have shown, al-Qaeda has not abandoned its intent to attack the United States, and indeed continues to attack us. Thus, in this ongoing armed conflict, the United States has the authority under international law, and the responsibility to its citizens, to use force, including lethal force, to defend itself, including by targeting persons such as high-level al-Qaeda leaders who are planning attacks. As you know, this is a conflict with an organized terrorist enemy that does not have conventional forces, but that plans and executes its attacks against us and our allies while hiding among civilian populations.

On this view, Al Qaeda is committed to continuing to plan and execute attacks against the US, and the fact that such attacks occur periodically rather than continuously does not mean that they are not part of an ongoing armed conflict. Thus, a 2010 US Department of Justice Office of Legal Counsel (OLC) memo, quoting scholarly work, has stated that “’terrorist’” war “’does not consist of a massive attack across an international border, nor does it consist of one isolated incident that occurs and is then past.  It is a drawn out, patient, sporadic pattern of attacks.  It is very difficult to know when or where the next incident will occur.’”

The US position has drawn some criticism in the international law community.  One set of critics argues that Al Qaeda and associated terrorist groups are akin to transnational criminal organizations, against whom the US should be using law enforcement measures rather than military force.  As one international judge and scholar puts it, “In the language of international law there is no basis for speaking of a war on Al-Qaeda or any other terrorist group, for such a group cannot be a belligerent, it is merely a band of criminals.”

A second set of critics accepts that the US may be engaged in an armed conflict in certain areas in which intense hostilities are occurring, but not outside of these areas.  As one critic argues, “Outside the real wars of Afghanistan and Iraq, al Qaeda’s actions and our responses have been too sporadic and low-intensity to qualify as armed conflict.”  Finally, some maintain that terrorist groups are to diffuse and localized to characterize them as constituents of a single organization such as Al Qaeda or other entity. While such groups may be loosely affiliated, this does not mean that they constitute a single enemy in a single armed conflict.

US assertion that it is engaged in an armed conflict thus raises questions that generally do not arise with respect to the conflicts between states that were the impetus for the creation of IHL. Can an armed exist without intense levels of violence on a continuous basis?  Can engagement in ongoing planning of attacks constitute involvement in an armed conflict, even if there may be long intervals between such attacks? Can groups in a variety of locations be treated as members of a single enemy armed force on the basis of their participation in violence that furthers the aims of a larger group, even if they may be motivated by a variety of disparate purposes?

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2  Where is the Battlefield?

If the US and its allies are engaged in an armed conflict against certain international terrorist groups, what constitutes a battlefield in that conflict?  This question matters because the answer determines where IHL permissions govern the use of force. Where this is the case, force may be used as a first resort against persons deemed enemy combatants, and it is permissible to cause civilian casualties as long as they are not excessive compared to the military advantage gained from the use of force.

The US position is that the conflict exists anywhere that members of groups covered by the AUMF are planning and launching attacks against the US.  The OLC has stated, “W]hen one of the parties to an armed conflict plans and executes operations from a base in a new nation, an operation to engage the enemy in that location” is legally authorized.  Thus, for instance, in concluding that legal authority existed to conduct a drone strike against a target in Yemen, OLC noted that the target was a leader of Al Qaeda in the Arabian Peninsula (AQAP) and that Yemen was a location in which “AQAP has a significant and organized presence, and from which AQAP is conducting terrorist training in an organized manner and has executed and is planning to execute attacks against the United States.” Such activities do not constitute a separate armed conflict in Yemen, but are hostilities being conducted as part of the larger conflict with designated terrorist groups.

Consistent with this, the US Attorney General stated in 2012, “We are at war with a stateless enemy, prone to shifting operations from country to country.   Over the last three years alone, al Qaeda and its associates have directed several attacks – fortunately, unsuccessful – against us from countries other than Afghanistan.”   Similarly, the General Counsel of the Department of Defense noted in that same year that “over the last 10 years al Qaeda has not only become more decentralized, it has also, for the most part, migrated away from Afghanistan to other places where it can find safe haven.” All such places in which terrorist attacks against the US are continuously being planned are battlefields in the armed conflict.

The territorial scope of the armed conflict between the US and certain terrorist groups has been a source of much debate and contention within the international law community.  Critics of the US position argue that the expansive permissions for the use of force under IHL should apply only where conditions in a particular state satisfy the criteria for an armed conflict.  From this perspective, the US may be engaged in conflicts with Al Qaeda and associated forces in certain locations in the world, but not in a single conflict that is global in scope.  Otherwise, critics argue, countries enjoying relatively peaceful conditions risk becoming conflict zones in which targeting based on the law of war applies.  With the dispersion of terrorists across several countries, this would considerably expand the geographical scope of military violence that could be lawfully inflicted.

The question where the US armed conflict with Al Qaeda and associated forces is occurring thus raises several questions. Must a sufficient level of hostilities exist in a state before it can be considered a battlefield in an armed conflict where IHL applies?  If so, what type of activity suffices?  Must it qualify as an armed conflict?  Or is it sufficient that ongoing planning and launching of terrorist attacks be conducted from a state, even if there is not open armed conflict?  This leaves aside for the moment the question whether, even if the use of force is authorized within a state, this state must consent to any use of force within its territory.

Notwithstanding the US position that it has expansive authority to proceed under IHL, in May 2013 the Obama administration announced a Presidential Policy Guidance (PPG) that imposed limitations on the exercise of that authority in areas outside of “active hostilities.”  The PPG is clear that an area of active hostilities need not be one in which the criteria for an armed conflict have been satisfied.

In areas outside of active hostilities, the use of lethal force is authorized only against persons presenting a “continuing imminent threat to US persons.”  In addition, such force may be used only when capture is infeasible, and there must be “virtual certainty” that an operation would not cause civilian casualties. These restrictions are adopted as a matter of policy; the US continues to maintain that it otherwise could use force under IHL in areas in which terrorists are planning attacks against the US. As of December 2016, the US regarded itself as engaged in active hostilities in Afghanistan, Iraq, Syria, and certain parts of Libya.  The restrictions in the PPG therefore do not apply to operations in these areas.  While the Trump administration has expressed some concern that the PPG is too restrictive, it has not yet formally revised it.

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3  Which Groups are the Enemy?

Which if any terrorist groups may be analogized to allies in a conventional interstate conflict such as the two World Wars, such that force can be used against any of their members under IHL?  The US takes the position that certain terrorist groups that have joined Al Qaeda’s campaign against the US fall into this category of “co-belligerents,” but this position has not gained complete acceptance.

While the US initially asserted in 2001 that it was engaged in an armed conflict with Al Qaeda and the Taliban, it has since declared that it is an armed conflict also with the Islamic State and Al Shabaab.  The basis for this position is that the AUMF does not identify specific parties against whom the President is authorized to use military force, but provides authority against any group that “planned, authorized, committed, or aided” the 9/11 attacks, or “harbored” any such group, in order to prevent future terrorist attacks on the US.

The US argues that this includes not only Al Qaeda but any forces “associated with” it.  It defines such associated forces as any group that “(1) is an organized, armed group that has entered the fight alongside al-Qa’ida and (2) is a co-belligerent with al-Qa’ida in hostilities against the United States or its coalition partners.”

In litigation involving Guantanamo detainees, the Justice Department explained in a court filing in 2009 that the US position is based on the concept of “co-belligerents” to a conflict: “The United States has authority to detain individuals who, in analogous circumstances in a traditional international armed conflict between the armed forces of opposing governments, would be detainable under principles of co-belligerency.”  A scholar and former Department of Defense lawyer has elaborated on this concept, “If ‘State A’ attacked the United States and ‘State B’ later allied with State A as a co-belligerent, the United States would be at war with both of them and it would be lawful for the US to use force accordingly. Specifically, the United States could target and detain members of State B’s armed forces.”

With respect to the Islamic State, a United States official has stated:

The 2001 AUMF has authorized the use of force against the group now called ISIL since at least 2004, when bin Laden and al-Zarqawi brought their groups together. The recent split between ISIL and current al-Qa’ida leadership does not remove ISIL from coverage under the 2001 AUMF, because ISIL continues to wage the conflict against the United States that it entered into when, in 2004, it joined bin Laden’s al-Qa’ida organization in its conflict against the United States. As AQI, ISIL had a direct relationship with bin Laden himself and waged that conflict in allegiance to him while he was alive.

One US official has explained that for a group to be considered a co-belligerent, it “must not only be aligned with al Qaeda. It must have also entered the fight against the United States or its coalition partners. Thus, an ‘associated force’ is not any terrorist group in the world that merely embraces the al Qaeda ideology. More is required before we draw the legal conclusion that the group fits within the statutory authorization for the use of military force passed by the Congress in 2001.”

One criticism of the US position is that the 2001 was not intended to encompass groups such as the Islamic State and Al Shabaab that were not in existence at the time of those resolutions, regardless of their current relationships with Al Qaeda. President Obama proposed an AUMF specifically to address this concern, but Congress did not accept his invitation to pass it.  Congress continues to debate this issue, which primarily involves the President’s authority under US law to target members of these groups.  To the extent that the President does not have domestic authority to engage in such operations, however, authority under international law would be lacking as well.

A second criticism of the US position asserts that the concept of co-belligerency is based on a flawed analogy to relationships between states. The paradigm case of co-belligerency is when multiple states declare war in support of a common cause, as with the Allied and Axis coalitions in World War II. In such cases, it is easy to see that a state that is a member of one coalition may attack a state that is a member of the opposing one.  Non-state terrorist groups, however, typically do not have a centralized authority structure that issues comparable formal proclamations that squarely align the interests of one group with another.  The fact that one group may share some aims with another, the argument goes, does not mean that is it an ally in the robust sense that is characteristic of conflicts between states.

Critics argue that it is important to be wary of assigning co-belligerent status too easily because it has the potential to result in a claim that there is a single armed conflict with groups across a large part of the world, rather than with specific terrorist groups with their own agendas in particular locations.  This ostensibly would obviate the need to demonstrate that using force under IHL is justified in each particular state, on the ground that justification for reliance on IHL has been satisfied once the existence of a single multi-state armed conflict has been established.

The issue therefore is whether the US is engaged in multiple armed conflicts with specific terrorist groups, or in a single conflict on the ground that all such groups can be treated as fighting under one banner.

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4  Who are Combatants?

Combatants in armed conflicts may be targeted with lethal force at any time on the basis of their status as combatants, regardless of their conduct at the time. The Geneva Conventions do not define who constitutes a combatant in conflicts between states and non-state groups.

The US maintains that anyone who regularly is involved or participates in activities of a non-state group involved in an armed conflict with the US is a member of that group who may be targeted as a combatant.  Specifically, it argues that it has the legal authority under IHL to kill or detain anyone who is “part of” al-Qaeda, the Taliban, or associated forces.  As the discussion above indicates, the latter includes the Islamic State and Al Shabaab.  Being part of such a group may involve formal membership or “participating sufficiently in its activities” to support such an inference.

The US Department of Defense Law of War Manual Section 5.7.3 maintains that a person can be part of a non-state armed group based on either formal or functional membership.  Formal membership may be reflected in official recognition or documents, but often will indicated instead through behavior such as:

  • acting at the direction of the group or within its command structure;
  • performing a function for the group that is analogous to a function normally performed by a member of a State’s armed forces;
  • taking a direct part in hostilities, including consideration of the frequency, intensity, and duration of such participation;
  • accessing facilities, such as safehouses, training camps, or bases used by the group that outsiders would not be permitted to access;
  • traveling along specific clandestine routes used by those groups; or
  • traveling with members of the group in remote locations or while the group conducts operations

With respect to functional membership, “[a]n individual who is integrated into the group such that the group’s hostile intent may be imputed to him or her may be deemed to be functionally (i.e., constructively) part of the group, even if not formally a member of the group.”  This functional integration permits an inference that a person “shares the group’s intention to commit hostile acts,” and distinguishes him or her from someone who is “merely sympathetic to the group’s goals.”  Evidence of functional membership may include:

  • following directions issued by the group or its leaders;
  • taking a direct part in hostilities on behalf of the group on a sufficiently frequent or intensive basis; or
  • performing tasks on behalf of the group similar to those provided in a combat, combat support, or combat service support role in the armed forces of a State.

The US position is that an individual may be considered part of an organized armed group regardless of the function that they perform “because the organization’s hostile intent may be imputed to an individual through his or her association with the organization.”  In addition, “the individual, as an agent of the group, can be assigned a combat role at any time, even if the individual normally performs other functions for the group.”

The US position reflects a more expansive definition of a non-state combatant that offered by the International Committee of the Red Cross (ICRC) in its Interpretive Guidance on Direct Participation on Hostilities.  That organization defines combatants as persons who perform a “continuous combat function” for an organized armed group, but not persons who perform support functions except with respect to specific hostile operations.  The former includes persons who plan, command, or execute hostilities on an ongoing basis.  It excludes persons such as those who “continuously accompany or support an O[rganized] A[rmed] G[roup],” but whose function does not involve direct participation in hostilities.  These latter persons are regarded as civilians providing support functions to an OAG, such as recruiters, trainers, financiers who contribute to the general war effort, and those who purchase, smuggle, manufacture, and maintain weapons “outside specific military operations.”

There has been considerable debate about both the US and ICRC approaches to defining non-state combatants, with the former criticized as overinclusive and the latter as underinclusive. That debate is handicapped to some extent by the lack of information about the type of intelligence that is used in specific instances to make a determination of combatant status and the level of certainty that is required.  This reflects the broader difficulty that the application of armed conflict standards for the use of force against non-state actors is a process that is intensely intelligence-driven.  It requires analysis and interpretation of “pattern of life” data on an individual as the basis for classifying a person as a combatant in an armed conflict who can be targeted at any time. This means that there are limits to the information that can be disclosed with regard to the basis for targeting in any specific instance.

The US and ICRC definitions essentially reflect different tradeoffs with respect to how far back in the causal chain of activities it is appropriate to regard someone as a combatant subject to lethal force.  The US maintains that a terrorist organization has one animating hostile purpose, and that anyone who regularly contributes to it should be regarded as subject to the use of force because he or she shares that purpose.  The ICRC narrower definition of combatant implicitly reflects the belief that a definition that may be underinclusive in some cases is appropriate because it minimizes the risk of innocent persons being erroneously identified as combatants subject to lethal force based on insufficiently robust intelligence.

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5  State Consent

Even assuming that conditions authorizing the use of military force under IHL exist in a given state, Article 2(4) of the UN Charter prohibits the threat or use of force against the political independence or “territorial integrity” of another state. The most straightforward way for a state to comply with Article 2(4) is to obtain the consent of the state in which it wishes to conduct operations as part of an armed conflict.  What if the latter state refuses such consent?

The US takes the position that it is entitled to use force notwithstanding the absence of state consent if a state is “unwilling or unable” to take steps to stop the threat to the US that is emanating from that state.  The US argues that this standard is “an important application of the requirement that a State, when relying on self-defense for its use of force in another State’s territory, may resort to force only if it is necessary to do so—that is, if measures short of force have been exhausted or are inadequate to address the threat posed by the non-State actor emanating from the territory of another State.” The White House Report on the Legal Frameworks Guiding the United States’ Use of Military Force and Related National Security Operations (White House Frameworks) Section II-B-4 elaborates on this test:

With respect to the “unable” prong of the standard, inability perhaps can be demonstrated most plainly where, for example, a State has lost or abandoned effective control over the portion of its territory where the armed group is operating. With respect to the “unwilling” prong of the standard, unwillingness might be demonstrated where, for example, a State is colluding with or harboring a terrorist organization operating from within its territory and refuses to address the threat posed by the group.

Reliance on this test has generated considerable discussion in the international law community, with some expressions of concern about a state that wishes to use force being ostensibly authorized to make a unilateral determination of whether another state that refuses consent to do so within its territory meets the standard.  To date, the US has relied on this approach only with regard to states in which there is a failed government, such as Somalia, or where governmental authority is contested and one side arguably is sympathetic to Al Qaeda, such as recently in Yemen.  This has quelled at least some concern, and many, although not all, observers now appear to accept the test as long as the standard is a stringent one and robust evidence is presented that it has been met.

Some states may consent to US operations in their territory, but may not wish publicly to acknowledge this fact. This appears to have been the case at various times with respect to targeted strikes in certain parts of Pakistan and Yemen, for instance.  In such cases, the US may conduct targeting as a covert action conducted by the Central Intelligence Agency rather than armed forces, which avoids the need to publicly acknowledge the operation or US responsibility for it.

A covert action is defined as “an activity or activities of the United States Government to influence political, economic, or military conditions abroad, where it is intended that the role of the United States Government will not be apparent or acknowledged publicly.” As long as this is the intention at the time of the operation, the fact that the US later may announce the fact of such an operation does not bring it outside the category of covert action.

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6  Detention

IHL rules governing detention were drafted with inter-state conflicts in mind.  They authorize the detention of combatants in an armed conflict for the duration of hostilities.  As a conceptual matter, such detention is not punitive, but a means to keep enemy combatant from returning to the battlefield. At the end of hostilities, combatants are to be returned to each side.

An armed conflict against terrorist groups presents challenges to this type of detention. There may be no formal cessation of hostilities, and groups or individuals may be engaged on a continuing basis to plot terrorist attacks even if they may diminish in number and intensity. Furthermore, as traditional foes such as Al Qaeda may be degraded, other groups may emerge that are characterized as “associated forces” because they have entered hostilities alongside Al Qaeda or can trace their pedigree to it.  In these respects, the duration of hostilities may be indefinite, which creates the prospect that someone who is detained as a combatant will be in confinement for the rest of their life.

The White House Frameworks in Section III-A state that the US regards itself as authorized to detain as enemy combatants “those persons who were part of, or substantially supported, Taliban or al-Qa’ida forces or associated forces that are engaged in hostilities against the United States or its coalition partners, including any person who has committed a belligerent act, or has directly supported hostilities, in aid of such enemy armed forces.” Drawing on a court ruling, the US asserts that relevant considerations regarding whom it may detain include “whether (1) the individual intended to fight against the United States or its coalition partners; (2) the individual closely associated with members of enemy forces; (3) other members of the enemy forces or documents created by the enemy forces identified the individual as a member; (4) the individual trained in a camp associated with an enemy force; (5) the individual stayed at a guesthouse associated with an enemy force; (6) the individual followed practices associated with enemy forces, such as the practice of turning over passports and money; (7) the individual swore an oath of allegiance to an enemy force; (8) the individual hosted leaders of the enemy force; (9) the individual recruited or referred aspiring members to the enemy force; (10) the individual traveled along routes conventionally used by the enemy force; (11) the individual lied to interrogators or provided implausible explanations for his or her behavior; and (12) the individual possessed a weapon.”

The US has stated that “the concept of ‘substantial support’ could encompass individuals whose support for enemy forces makes them analogous to those who accompany the armed forces without actually being members thereof, such as civilian members of military aircraft crews or members of services responsible for the welfare of the armed forces.”

In 2011, President Obama established a process to assess whether continued detention of persons at Guantanamo Bay who are not facing criminal charges under domestic or international law, and are thus being detained solely as combatants under IHL authority, is necessary in order to “protect against a continuing significant threat to the security of the United States.” Executive Order 13567 established Periodic Review Boards (PRBs) whose purpose is to make this determination in hearings in which a detainee may participate. The Order emphasizes that such review is being established as a matter of policy, and that the US continues to maintain that it has the authority to detain combatants for the relevant non-state groups for the duration of hostilities. This review process, however, reflects recognition of the potentially severe consequences of relying on such detention with respect to persons designated as members of terrorist organizations.

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7  Conclusion

The US position that its counterterrorism campaign includes engagement in armed conflict against terrorist groups reflects the view that law enforcement measures are insufficient by themselves to address what the US regards as organized attempts to engage in terrorist attacks on the US. This approach requires applying traditional law of war principles in new ways, which has implications for a wide range of issues.  Some US extensions of these principles have garnered general support within the international community, while others have generated more criticism.  Given the challenges of applying to counterterrorism a regulatory scheme for armed conflict that was designed with inter-state conflict in mind, the debate is likely to be ongoing.

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