On February 24, Mexico convened an informal meeting of the United Nations Security Council to discuss, among other things, whether the UN Charter permits the use of armed force by one State against non-state actors on the territory of another State without the latter’s consent. Twenty-four hours later, the United States did just that, carrying out airstrikes in Syria against several small facilities used by Iraqi militias. It is not alleged that Syria directed, controlled, or even supported these militias, so they are “non-State actors” for the purposes of this essay.

Were the airstrikes lawful? Unsurprisingly, the United States thinks so, while Syria and Iran think not. Most States won’t say. That’s why the Feb. 24 meeting was interesting and important. By inviting States to express their legal positions in the abstract—rather than judge politically-charged incidents based on incomplete evidence—the meeting drew out a wide range of views that raise new questions and add urgency to old questions.

The Security Council published the written statements this morning. A full video of the meeting is available here (and below). This essay offers my own summary and legal analysis.

Restrictive Views


Brazil, China, Mexico, and Sri Lanka categorically rejected the use of force against non-State actors without the consent of the territorial State. China’s statement was perhaps its strongest to date:

The use of force against non-state actors in the territory of another state, which is for the purpose of self-defence, shall be subject to the consent of the state concerned. No state should interfere in other’s internal affairs under the cloak of “counter-terrorism” or use force arbitrarily in the name of “preventive self-defence.”

These States fall squarely into the “restrictive” camp.

Intermediate Views


Austria took the intermediate position that it may be lawful to use force against a non-State actor if the territorial State is “unable, as a consequence of the complete absence of State authority and effective control over the respective territory, to prevent or suppress [the group’s] operations.” Notably, Belgium took a similar position in the past, but at the Feb 24 meeting stated that “States can have recourse to self-defense in case of attacks perpetrated by non-State actors … that are located on the territory of a sovereign State.”

Expansive Views


Australia, Azerbaijan, Belgium, Denmark, Estonia, the Netherlands, Turkey, the United Kingdom, and the United States asserted a broad right to use force in self-defense against non-State actors in the territory of another State. These States fall into the “expansive” camp, but important differences remain. For example, in its statement,

Australia recognizes that the right to exercise individual or collective self-defense is available against non-state actors in the territory of another State, where those actors are involved in carrying out an actual or imminent armed attack, and where the territorial State is unwilling or unable to prevent such attacks originating from its territory.

Estonia, the Netherlands, and the United Kingdom also stated that force may be used in self-defense only against an actual or imminent attack. Turkey alluded to imminent attacks and threats as well. In contrast, the United States stated that “the exercise of the inherent right of self-defense is subject to the customary international law requirements of necessity and proportionality,” but did not mention any requirement of imminence. In 2016, the United States took the position that,

once a State has lawfully resorted to force in self-defense against a particular armed group following an actual or imminent armed attack by that group, it is not necessary as a matter of international law to reassess whether an armed attack is imminent prior to every subsequent action taken against that group, provided that hostilities have not ended.

In other words, the imminence of an armed attack is legally relevant only to a ‘first strike’ against a non-State actor, not to military operations following an armed attack. This likely explains why the United States did not claim that its Feb 25 airstrikes in Syria halted an imminent armed attack. On the U.S. view, it was enough to allege that an armed attack had already occurred.

Note that Australia asserts the right to use force “where the territorial State is unwilling or unable to prevent such attacks originating from its territory.” Similarly, the Netherlands also stated that “the right to self-defense can also be invoked …. where the state from which the non-state actors’ attack originates is unwilling or unable to stop the armed attack.” In its Feb 24 statement, the United States referred to the “threat emanating” from the territory of a State which was unwilling or unable to “take effective measures to confront a non-State actor that is using the State’s territory as a base for attacks and related operations.” (See also here.) However, in its report to the UN Security Council following the Feb 25 airstrikes, the United States referred only to the “use” of Syrian territory by Iraqi militia and Syria’s unwillingness or inability to prevent that “use” of its territory, without suggesting that any attacks originated from Syria’s territory or that Syria was unwilling or unable to prevent future attacks.

The Netherlands also stated the common view that “the use of force must have a certain scale and effects in order to constitute an armed attack. It must consist of more than isolated incidents, terrorist or not.” In contrast, the United States takes the highly unusual view that any illegal use of force constitutes an armed attack and triggers the right of self-defense.

Finally, the Netherlands stated that “it is important to establish the existence of an armed attack or an imminent armed attack,” adding that “self-defense should be necessary to counter the armed attack and be proportionate in relation to this attack.” The Netherlands continued:

In principle, the same criteria apply to establishing the end of an armed attack as to the beginning. We are of the view that a State has some margin of appreciation to determine whether the armed attack has really ended, or whether there is merely a temporary lull.

In other words, if an armed attack is clearly over, and no further armed attack is imminent, then force is prohibited and alternatives must be sought. If an armed attack is not clearly over, then the use of force may be excused—even if it turns out that the attack was in fact over. In contrast, the United States takes the view that, even if an armed attack is clearly over, force remains lawful so long as further attacks are anticipated (though not imminent, as we have seen).

To sum up, the United States seems to occupy an extreme position even within the “expansive” camp. It alone appears to assert a right to use cross-border force when no ongoing or imminent armed attack originates from another State’s territory. Other members of this camp indicate that cross-border force may be used only to halt or repel an ongoing or imminent armed attack originating from another State’s territory which that State is unwilling or unable to prevent.

Ambiguous Views


France, India, and Russia made statements that are hard to classify, though for different reasons. So did Norway, Pakistan, Qatar, and St. Vincent and the Grenadines.

In 2019, France stated that,

In accordance with ICJ case law, France does not recognize the extension of the right to self-defense to acts perpetrated by non-state actors whose actions are not attributable, directly or indirectly, to a State.

France has, in exceptional cases, invoked self-defense against an armed attack perpetrated by an actor having the characteristics of a “quasi-State,” as with its intervention in Syria against the terrorist group Daesh (ISIS/ISIL). However, this exceptional case cannot constitute the definitive expression of recognition of the extension of the concept of self-defense to acts perpetrated by non-state actors acting without the direct or indirect support of a State.

In other words, France recognized the extension of the right of self-defense, but only in exceptional cases to acts perpetrated by a “quasi-State.” This position placed France just outside the “restrictive” camp. However, on Feb 24, France stated that

While the victim of attack must be a State, according to Article 51 [of the UN Charter], the status of the aggressor is not delimited or defined. Unfortunately, some non-state groups, particularly terrorist groups, now have the means to commit acts that amount to armed attack against States. …

This statement makes no reference to exceptional cases or to quasi-States. It appears to extend the right of self-defense to any non-state group with the means to commit violent acts of sufficient gravity. While I suspect that the Feb 24 statement was not meant to announce a change to France’s 2019 position, it is possible that France has moved closer to the “expansive” camp.

India stated that:

Article 51 is not confined to “self-defense” in response to attacks by states only. The right of self-defense applies also to attacks by non-state actors. …

6. Non-state actors such as terrorist groups often attack states from remote locations within other host states, using the sovereignty of that host state as a smokescreen. In this regard, a growing number of States believe that the use of force in self-defense against a non-state actor operating in the territory of another host State can be undertaken if:

i. The non-state actor has repeatedly undertaken armed attacks against the State
ii. The host State is unwilling to address the threat posed by the non-state actor.
iii. The host State is actively supporting and sponsoring the attack by the non-state actor.

7. In other words, a State would be compelled to undertake a pre-emptive strike when it is confronted by an imminent armed attack from a non-state actor operating in a third state. This state of affairs exonerates the affected state from the duty to respect, vis-a-vis the aggressor, the general obligation to refrain from the use of force.

It is not entirely clear whether the three listed conditions are meant to be conjunctive or disjunctive, that is, whether self-defense is permitted if any condition is satisfied or only if all three conditions are satisfied. Both interpretations are awkward. On balance, the listed conditions are most likely conjunctive. The last quoted sentence tips the balance: the general obligation to refrain from the use of force is owed to the territorial State, but does not apply because the territorial State has made itself “the aggressor.” Since only supporting or sponsoring an attack could make the territorial State “the aggressor,” that condition must be satisfied before force may be used. For a different interpretation, see here.

Russia stated that:

The issue of the use of article 51 against non-state actors is a difficult one, because this article was not intended for this purpose. We must recognize that. It was drafted in order to describe the right of self-defense against armed attacks of States. However the language of this article allows for a broader interpretation. This broader interpretation became practical after 9/11, which demonstrated that an attack of terrorists may rise to the level of an armed attack of a State. It was confirmed in SC resolution 1368 (2001).

However, it does not mean that any terrorist attack in a cross border context gives rise to the right of self-defense. Firstly, the criteria applicable to the definition of an armed attack must be fulfilled, in particular in terms of the magnitude of the event. Secondly, the position of the government of a State from whose territory terrorists strike must be carefully assessed. It is one thing when a government directs and supports such an attack and another if it uses all available means to fight such terrorists and is open for cooperation with other States. In the latter case it is obvious that cooperation and consent of the government must be requested. The level of bilateral relations or lack thereof may not be the ground for avoiding this requirement.

In other words, if the territorial State is willing to fight non-state actors on its territory but unable to defeat them on its own, then its cooperation and consent must be requested. What if such a territorial State arbitrarily refuses to consent or cooperate? The Russian statement doesn’t say. In contrast, the United States takes the position that, if the territorial State is unwilling or unable to effectively confront the non-State actor in its territory, then force may be used without its consent. Presumably, other members of the anti-ISIL coalition that carried out military operations in Syria without requesting its consent share the U.S. view. This difference seems sufficiently important to place Russia just outside the “expansive” camp.

Norway’s 2013 law of armed conflict manual (translated into English in 2018), stated that

The prohibition against the use of force also influences a state’s ability to use armed force against non-state entities in the territory of another state. The use of force against non-state entities without the permission of the state in which these entities are located may thus constitute an infringement of that state’s sovereignty.

However, on Feb 24, Norway stated that

While Article 51 is focused primarily on attacks committed by other states, we believe there is a basis in international law to a limited right to use force in self-defense against such attacks, in certain exceptional situations.

Norway then noted its participation in the anti-ISIL coalition. Perhaps Norway has simply joined the “expansive” camp. However, given its previous statements, it’s possible that Norway takes an intermediate position, much like France in 2019, which carves out an exception for ISIL due to its State-like organization and military capability.

Pakistan stated that it had refrained from using force against armed groups in a non-consenting State (presumably Afghanistan) but reserved the right to act in self-defense against the State sponsoring those armed groups (presumably India). If this statement reflects Pakistan’s legal position, then Pakistan falls close to the “restrictive” camp—but this is not clear. (Pakistan also rejected the legality of preventive self-defense.)

Qatar stated that

one must recognize that certain situations necessitate the use of force, notably in application of the inherent and legitimate right to self-defense, and to counter the serious threat posed by terrorist acts. There is indeed consensus that terrorist acts do pose serious threats to peace and security and have caused grave human suffering and social and economic impacts. Therefore, many Member States, including the State of Qatar as a responsible member of the international community, has taken part in collective action to fight common threats posed by UN designated terrorist groups, including firm and decisive action as necessary.

Qatar’s references to “threats to peace and security,” “collective action,” and “UN designated terrorist groups” make it unclear whether “the use of force … to counter the serious threat posed by terrorist acts” is legally justified by the right to self-defense alone, or depends on additional sources of legitimacy (compare here).

Finally, St. Vincent and the Grenadines stated that

To be sure, there are some contexts within which states may be compelled to use force to protect civilians, dispel non-state armed groups, and defend their sovereignty and territorial integrity.

This statement clearly places St. Vincent and the Grenadines outside the “restrictive” camp. However, the statement does not use the language of the UN Charter (“armed attack”), or the familiar terms of the debate (“unwilling or unable”), so it does not put St. Vincent and the Grenadines squarely in the “expansive” camp either.

Missed Opportunities


The remaining participants in the Feb 24 meeting either did not address the specific legal question (Armenia, Finland, Georgia, Iran, Ireland, Kenya, Liechtenstein, Ukraine) or said nothing from which their legal position can be reliably inferred (Ecuador, Peru, Syria, Tunisia, Vietnam). Understandably, several of these States have more pressing concerns. It is harder to understand why other States chose not to clearly express their legal position. Perhaps, after a decade of war in Syria, they still don’t have one.

Conclusion (or Lack Thereof)


In my view, the “restrictive camp” is legally correct. The UN Charter permits self-defense against an armed attack by another State (see here and here). That was the law in 1945, and subsequent practice in the application of the Charter has not established the agreement of the parties to a different interpretation. The division of opinion summarized above leaves the law unchanged. Be that as it may, the division of opinion is stark, and may be increasingly polarized. Belgium, France, and Norway may be moving from an intermediate position toward the “expansive” camp. That would be a pity. In my view, international law could be developed in a responsible way to extend the right of self-defense to non-state actors like ISIL that posed exceptionally grave threats to other States like Iraq. Unfortunately, only States can develop international law, and most can’t be bothered.