Analyzing State Support to Non-State Actors – Part II: Response Options and Conflict Classification
As non-State actors assume an increasingly prominent role in international affairs, State support to them as a strategic tool for advancing political objectives has become more common. Such support presents significant challenges to the clear-eyed application of international law.
A salient example can be seen in the ongoing attacks by the Iranian-backed Houthis in the Red Sea, an example we’ll return to throughout. Despite substantial evidence of Iran’s support for Houthi operations, the precise nature and extent of this relationship remain deliberately obfuscated (see, e.g., here and here). The fact that relevant legal concepts, such as “attribution” and “control,” bear distinct meanings depending on the body of law under which they are being applied further compound the legal complexity.
In this two-part series, we provide a normative framework for analyzing State support to non-State actors engaged in hostile conduct against another State. In Part I, we identified situations in which a State can be deemed in violation of international law, either based on its own conduct in supporting a non-State actor or because of legal attribution of a non-State actor’s conduct to the State.
In this part, we turn to the final two legal questions addressed by this framework. We begin by outlining the responses available to the victim State, labeled the “injured State” under the law of State responsibility. Finally, we explain when support by one State to a non-State actor engaged in hostilities with another State triggers an international armed conflict (IAC) between the two States.
Response Options
International law contemplates an array of response options for injured States facing international law violations (“internationally wrongful acts”), a subject discussed in Part I. Four loom large: retorsion; countermeasures; necessity; and self-defense.
Retorsion
States are always entitled to engage in acts of retorsion, which are actions or omissions that may be unfriendly but do not violate any primary rule of international law. For instance, other States may impose economic or diplomatic sanctions in response to a State’s support of non-State actors. Such sanctions are, except in extreme cases, at the discretion of the State taking them, and there is no condition that they be in response to an internationally wrongful act. Take the case of a non-State actor engaging in a misinformation campaign directed at one State using cyber infrastructure located in another with the latter’s acquiescence. Engaging in a misinformation campaign, except in limited circumstances (see Milanovic & Schmitt), does not violate international law. Nevertheless, the victim State would be entitled to respond with acts of retorsion directed at the latter.
Countermeasures
While an internationally wrongful act by another State is not a condition precedent to retorsion, it is for the taking of countermeasures under the law of State responsibility (Articles on State Responsibility (ASR), art. 22; on the ASR, see Part I of this series). A countermeasure is an act (action or omission) that would violate international law but for the fact that it is either intended to compel a State violating international law to desist or designed to secure reparations (see below) from the latter State. Thus, if a State’s support to a non-State actor violates a primary rule of international law or if it is responsible for unlawful acts by a non-State actor, the injured State is entitled to respond in a way that would otherwise be unlawful (see ASR, Ch. II). Under the law of State responsibility, the fact that an act qualifies as a countermeasure is a so-called “circumstance precluding wrongfulness” (see ASR, Ch. V).
Consider the case of one State providing support to rebels in another State. If doing so would run afoul of the prohibition on intervention, it would be lawful for the “injured State” to, for instance, close its territorial sea to innocent passage by all vessels flagged in the first State. This is so even though the law of the sea undeniably affords a right of innocent passage to the vessels of all States (Law of the Sea Convention, art. 17, and customary law). Alternatively, consider a situation in which an insurgent group operates from one State’s territory into another. The victim State asks the territorial State to put an end to those operations, but it does not, even though it could easily do so; it is passively supporting the group. Assuming the existence of a rule of due diligence, as we do, the territorial State would be in breach of that obligation, thereby justifying countermeasures by the victim State against the territorial State designed to compel its compliance with that obligation.
It must be cautioned that the taking of countermeasures is subject to strict conditions and restrictions. For instance, the countermeasure must be proportionate to the harm the injured State is suffering, and it may not involve the use of force, a remedy available only in the case of Security Council authorization or self-defense (see ASR, arts. 50-51).
Finally, as noted, an injured State may use countermeasures to secure any reparations that are appropriate in the circumstances. Reparations may take the form of compensation, satisfaction, restitution, or a combination thereof. The customary law nature and requirements for reparations are restated in the ASR (art. 31).
Necessity
A third response option is to act pursuant to the plea of necessity. The plea of necessity is available to respond to a situation in which an “essential interest” of the State is facing “grave and imminent peril,” and the action necessary to address the situation, although otherwise unlawful, is the only means of doing so (ASR, art. 25). In the context of State support to non-State actors, cases in which necessity would provide a basis for action are rare but not entirely out of the question.
Consider a situation in which State A is shipping weapons through State B to an insurgent group in State C. Although State B is not supporting the operation in any way, it lacks the resources to end the transshipment. For geopolitical reasons, State B is unwilling to consent to State C’s action on its territory to remedy the situation. State A is in violation of the prohibition on intervention, but State B is not in violation of its due diligence obligation because there are no feasible means at its disposal to put an end to the transshipment, and States are not obligated to consent to assistance by other States to comply with a due diligence obligation.
State C would be entitled to conduct cyber operations to disable transportation hubs reasonably believed to be involved in the transshipment even though its actions would constitute, by the prevailing view among States, a violation of State B’s sovereignty. The fact that the cyber operations are the only way to put an end to the transshipment, which self-evidently constitutes a “grave and imminent peril” to State C’s “essential interest,” empowers it to engage in the operation on the basis of necessity.
Self-Defense
Although it is questionable whether or not the right of self-defense against armed attacks provided for in Article 51 of the UN Charter and customary international law applies to attacks by non-State actors operating autonomously, we are of the view, and it is the position of the United States, that it does (U.S. DoD, Law of War Manual, §1.11.5.4). In this regard, note that this is not a universally shared view (see Haque; Hakimi; Armed Activities, para. 146; and Wall, para. 139). For our purposes, however, the question is whether a State’s support to a non-State actor engaging in hostilities at the level of an armed attack allows the victim State to defend itself by conducting operations against the supporting State (in addition to the non-State actor).
In limited circumstances, it can, subject to the conditions of necessity and proportionality (U.S. DoD, Law of War Manual, §1.11.1.3 and §1.11.1.2). This is so in situations involving “‘the sending by or on behalf of a State of armed bands, groups, irregulars or mercenaries, which carry out acts of armed force against another State of such gravity as to amount to’ (inter alia) an actual armed attack conducted by regular forces, ‘or its substantial involvement therein’” (Paramilitary Activities, para. 195). In so concluding, the ICJ drew upon the UN General Assembly’s Definition of Aggression resolution (Annex, art. 3(g)). Note that this standard must be distinguished from the “effective control” standard used to attribute the actions of non-State actors to a State for the purposes of the law of State responsibility. Here, the ICJ’s standard must be understood solely as a “circumstance precluding wrongfulness” under the law of State responsibility that allows the injured State to resort to force against the supporting State in order to defend itself.
The key in the situations considered in this post is the reference to “substantial involvement therein.” This is a somewhat ambiguous standard, but it does not encompass support that the Court excluded from the reach of the use of force prohibitions, specifically “the provision of weapons or logistical or other support” standing alone (para. 195). On the other hand, we are of the view that providing intelligence enabling a series of attacks on specific targets would reach that level.
Consider, for instance, Iran’s support to the Houthis rebels. In addition to the provision of finances (here), weapons (here), and training (here), Iran is purportedly providing the Houthis with real-time targeting intelligence via its spy vessels in the Red Sea and Gulf of Aden (see, e.g., here, here, here, and Pedrozo). But for the support of these Iranian auxiliary intelligence ships, the Houthis could not engage in some of their hostile operations. In our estimation, if confirmed, Iran’s conduct constitutes “substantial involvement” in ongoing Houthi attacks. This is so regardless of whether Iran has any particular level of “control” over Houthi forces.
The prevailing view of international law is that an armed attack is “the most grave form” of a use of force, such that not all uses of force amount to armed attacks (Paramilitary Activities, para. 191). Indeed, when excluding “the provision of weapons or logistical or other support” from qualification as an armed attack, the Court noted that it “may be regarded” as a use of force (para. 195). Thus, a State’s support might be an internationally wrongful act in that it violates the use of force prohibition but not trigger the right to respond forcibly against the supporting State.
However, it must be cautioned that the United States holds the position that all unlawful uses of force are armed attacks triggering the right of self-defense (U.S. DoD, Law of War Manual, §1.11.5.2). By this view, support to a non-State actor that qualifies as a use of force in the manner described above would trigger the victim State’s right to respond forcibly in self-defense against the supporting State.
It is essential to understand that each of the response options set forth above is unique. Acts of retorsion are always available to one State against another State when the latter supports a non-State actor in any way. Indeed, acts of retorsion are available for any reason or no reason at all, for they are, by definition, lawful. In contrast, the taking of countermeasures against a State providing support requires that the provision of the support violates a primary rule of law or that the actions of the non-State actor breach an obligation owed by the supporting State and those actions are attributable under the law of State responsibility to it as a matter of law (see Part I). The plea of necessity is only available as a circumstance precluding the wrongfulness of a State’s response in extreme circumstances in which an essential interest of the State is at risk due to another State’s support to a non-State actor, and responding in an otherwise unlawful manner is the only way to remedy the situation. However, there is no requirement that an internationally wrongful act has been committed. Finally, except in cases in which the UN Security Council has authorized the use of force (see Ch. VII), only self-defense in the face of a use of force at the armed attack level by a non-State actor that has been conducted with the “substantial involvement” of a State entitles the use of force against that State.
Characterization of the Conflict
The previous sections examined when a State’s support to a non-State actor qualifies as a violation of international law by that State and cataloged remedies available to the injured State. However, it is also necessary to ask whether a State’s support to a non-State actor has triggered an IAC between it and the State against which the non-State actor is conducting operations (on this issue, see the analysis by Ferraro). There are two situations in which such support initiates such a conflict.
The first is a situation referred to as “internationalization.” The International Criminal Tribunal for the former Yugoslavia (ICTY) addressed internationalization in its very first case, Tadić. The question was whether the former Republic of Yugoslavia (FRY) exercised sufficient control over Bosnian Serb forces, an “organized armed group” (OAG) under LOAC, to qualify the situation as an IAC between the FRY and Bosnia and Herzegovina. The appellate chamber found that the conflict was an IAC based on the “overall control” FRY exercised over Bosnia Serb forces (Tadić, para. 146).
According to the ICTY’s Appeals Chamber,
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). … 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 (Tadić, para. 137; see also, e.g., Lubanga, para. 211; Kordic, para. 111).
Notably, overall control does not require the “issuing of specific orders by the State, or its direction of each individual operation” (Tadić, para. 137, emphasis added). Thus, the analysis requires a holistic consideration of the relationship between the supporting State and the OAG. Ultimately, the greater the supporting State’s involvement in the non-State actor’s operational planning and execution, the greater the likelihood that the overall control threshold will be met.
It is essential to distinguish the “overall control” test from the “effective control” test discussed in Part I of this series. They serve different purposes and, therefore, are separate and distinct. The overall control test simply serves to characterize a conflict for the purposes of the law of armed conflict and war crimes law. If the overall control test is met, an IAC exists between the two States such that the two States are parties to the conflict, and LOAC now governs relations between them that have a nexus to the conflict. Essentially, it is a “choice of law” test.
When the test is satisfied, the pre-existing non-international armed conflict (NIAC) is “internationalized” and LOAC applicable in an IAC supplants that which applies in a NIAC (although many provisions in the two bodies of law are similar and sometimes identical). The conflict between the non-State actor and the State is now part of the IAC between the supporting State and that State.
In contrast, the effective control test is used only to determine whether the actions of the non-State actor in question are attributable in law to the supporting State such that countermeasures may be taken against it, and it is, as appropriate, responsible for reparations. The ICJ acknowledged this distinction in the Bosnian Genocide case between Bosnia and Herzegovina and Serbia and Montenegro (paras. 402-07).
In our opinion, there is a second situation in which support to an OAG could trigger an IAC with the State against which the OAG is fighting. In it, the supporting State is not necessarily in overall control of the non-State actor. Consider the case where the OAG receives substantial support from a State but independently decides which operations it will and will not conduct.
We are of the view that it is appropriate to look to the following factors when assessing whether support, such as providing tactical or operational level intelligence, initiates an IAC. One of us (Schmitt), in the context of providing support to a State, has suggested consideration of the following factors when assessing whether support renders the supporting State a belligerent:
– An intent on the part of the supporting State to contribute to specific conduct of hostilities operations by the supported State or frustrate those of the State’s adversary;
– The extent to which the support benefits specific conduct of hostilities operations of the supported State or hinders those by its adversary;
– The degree to which the support is integral to specific conduct of hostilities operations of the supported State or defensive action against its enemy;
– The degree of immediacy between the provision of intelligence and its use.
Ultimately, the question is whether there is a “collective conduct of hostilities” by the supporting State and the OAG. Specifically, did the supporting State intend to directly support operations by the OAG that would have qualified as an IAC had those operations been conducted by the supporting State itself?
The classic example would be intentionally providing targeting intelligence without which an OAG could not have mounted specific attacks, when the State providing it, although knowing it was likely to be so used, had no role in planning or approving the relevant operations. Similarly, a State might give weapons to a non-State group to meet a particular tactical need, and those weapons are quickly put into service, but the supporting State does not have control over their specific use. In other words, the requisite control is absent, but the degree to which the support enables the operations is so high that the supporting State becomes a party to the conflict.
In such a case, the supporting State and the OAG are essentially co-belligerents, but whereas the supporting State is involved in an IAC, the OAG is still engaged in an NIAC because the “overall control” test has not been satisfied. This approach, which has not been considered in depth by the LOAC community, is a variant of the so-called “support-based approach” (2015 Challenges Report, p 19; 2019 Challenges Report; Droege and Tuck; Ferraro).
To put these questions of conflict classification in context, consider Iran’s support to the Houthi rebel forces. Presume, as we do, that based on the ongoing intensity of the conflict, the United States is engaged in a NIAC with Houthi rebels. The question becomes whether Iran’s support to the Houthis has triggered an IAC between the United States and Iran.
To assess whether Iran’s support has internationalized the conflict, we look to whether Iran exercises “overall control” of Houthi forces. Unsurprisingly, Iran has sought to publicly distance itself from Houthi operations, stating it “plays no role in setting [Houthi] national or operational policies.” While there is evidence to the contrary, Iran’s efforts to obscure its connection to the Houthis are an obstacle to reliably assessing its involvement in the “organizing, coordinating, or planning” of ongoing Houthi attacks, as is required to establish overall control. Even with greater transparency, it remains possible that the Houthis act autonomously from Iran in planning specific operations.
Assuming, arguendo, that Iran’s relationship with the Houthis is not of a nature to internationalize the conflict, its support may still be of a nature to trigger a separate IAC between it and the United States. Specifically, Iran’s use of auxiliary intelligence ships to provide real-time targeting information to Houthi operations may meet the threshold of this support-based approach. Ultimately, context matters. However, this real-world example demonstrates two circumstances under which State support might trigger an IAC and, with it, the law applicable to international armed conflict.
Conclusion
State support to non-State actors has become a defining feature of contemporary international relations, reflecting both the growing influence of non-State entities and the strategic utility they offer to States seeking plausible deniability. However, this development complicates the legal landscape. The increasing capacity of non-State actors to violate international norms, combined with the State-centric design of existing treaty law, poses significant challenges for legal assessment and accountability. The legal regimes, which often employ similar terminology with distinct meanings, further compound these difficulties.
This two-part post has sought to clarify these complexities by offering a normative framework for analyzing State support to non-State actors. Across the two parts, we examined the international legal standards applicable to four core questions: (1) when State support constitutes a violation of a primary rule of international law; (2) the conditions under which a State may be held responsible for the actions of a non-State actor; (3) the legal avenues available to a State injured by such support; and (4) the circumstances under which State support may give rise to an IAC. Hopefully, our normative framework will help State legal advisors navigate these choppy legal waters.
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Michael N. Schmitt is the G. Norman Lieber Distinguished Scholar at the United States Military Academy at West Point. He is also Professor of Public International Law at the University of Reading and Professor Emeritus and Charles H. Stockton Distinguished Scholar-in-Residence at the United States Naval War College.
Major Alex Hernandez is an active-duty Army judge advocate and a military professor assigned to the Stockton Center for International Law in Newport, Rhode Island.
The views expressed are those of the authors, and do not necessarily reflect the official position of the United States Military Academy, Department of the Army, or Department of Defense.
Articles of War is a forum for professionals to share opinions and cultivate ideas. Articles of War does not screen articles to fit a particular editorial agenda, nor endorse or advocate material that is published. Authorship does not indicate affiliation with Articles of War, the Lieber Institute, or the United States Military Academy West Point.
Photo credit: Voice of America
