• Johaira C. Wahab

Self-Defense Against NonState Actors & Recent US Military Strike in Syria: Considerations for the PH

Photo Source: Ivan Omar Hassib


On February 25, 2021, the US conducted a “targeted military strike” on a facility in Syria used by “Iran-supported non-state militia groups.”

According to President Biden’s letter to the US Congress, the attack was pursuant to the US’ “inherent right of self-defense as reflected in Article 51 of the UN Charter” and a “necessary and proportionate action” in response to attacks by said groups, which “targeted US and Coalition personnel” in Iraq. The letter cited an attack in Erbil on February 15, which wounded US service members and contractors working at a US-led military base, including a Filipino. It stated that the military action in Syria was intended to deter future attacks by said groups on the US and its partners.

It went on to say that although the groups were non-state actors “supported” by Iran, the US attack targeted the facility in Syria because the groups were located and continued to operate there, and the Syrian Government was “unwilling or unable to prevent the use of its territory by non-state militia groups responsible for [the attacks].”

Besides the War Powers Report and its Article 51 notification, the US Government has not issued any other statement clarifying its legal justification for the attack. Legal experts (read Haque, Hathaway, and Goodman) have raised questions about the lawfulness of the attack, particularly with respect to its necessity.

Use of Force in the Protection or Defense of Nationals Overseas

The February 15 attack in Erbil cited in President Biden’s letter (as well as in the Article 51 notification) was not the first time that a Filipino was caught in the midst of a terrorist act or otherwise hostile actions by armed groups overseas.

In July 2004, a Filipino truck driver was taken by Iraqi militants in Falluja and was only released after President Arroyo withdrew Philippine troops from the US-led military coalition in Iraq. In October 2004, a Filipino diplomat volunteering with the Joint Electoral Committee of the UN in Afghanistan was among UN staff abducted by the Taliban. He was released in November of the same year through the concerted efforts of the Philippine Department of Foreign Affairs and the United Nations negotiating for their release.

With millions of Filipinos overseas, Philippine security interests easily go beyond the bounds of its territory and extend to the protection of its nationals wherever they may be. Indeed, the protection of, or assistance to, its nationals is one of the key pillars of Philippine foreign policy.

The use of force in self-defense is a widely recognized exception to the prohibition on the use of force in Article 2(4) of the UN Charter. Under both treaty (Article 51 of the UN Charter) and customary international law, States have an inherent right to use force in self-defense in the occurrence of an armed attack against it. An armed attack against a State’s legitimate interests, such as its nationals, anywhere those interests may be located, can be deemed an armed attack on the State itself. Indeed, the right to forcibly protect one’s nationals has been argued to be a part of the inherent and customary right of self-defense.

The reference to the Filipino casualty in its Article 51 report could have been made by the US for a host of possible reasons, such as recognizing the Filipino contractor’s service to the base, indicating significance ascribed to the death of an ally’s national in the course of an attack on one of its bases, demonstrating the gravity or scale of the attack, or highlighting the multinational dimension of the attack. In any case, the mention of the contractor’s nationality does put the Philippines in, at the very least, a comparable position to that of the US, in terms of having been the subject of an armed attack by non-state armed militias.

One question that arises for the Philippines, being in said position, is whether, in its view, the US military strike in Syria was a lawful action by a State under international law in response to an attack that resulted in injury or death to its nationals overseas. That the Filipino who died in the Erbil attack was a civilian contractor working in a US military base at the time of the attack might also have to be factored in this analysis: While a State has the prerogative under international law to extend consular assistance to all its distressed nationals overseas, does a State also have the right of self-defense where the death or injury to its national arose in the course of, or as a result of, the latter’s employment in a foreign military base?

To be sure, the decision of States to engage in military actions overseas is also determined by considerations other than international law: some options may be lawful but not deemed feasible, nor even advisable, in certain circumstances due to political, military or economic realities between States concerned. In any case, international law remains to be a crucial factor, which determines the range of permissible State responses, informs diplomatic posturing or even military strategy, and enhances legitimacy and public acceptability of actions taken, especially for States whose constitutions affirm the primacy of the rule of law.

Another question which arises, in relation to the mention of the Filipino casualty, is whether the US is also relying on a theory of collective self-defense, on behalf of Iraq, the Philippines or even by some accounts, Saudi Arabia, aside from individual self-defense. In the Nicaragua decision, the ICJ noted that to justify a State’s exercise of a right of collective self-defense, the other State in whose behalf self-defense is being asserted must “believe that it was the victim of an armed attack” and “requested the assistance” of the State conducting the defensive use of force.

The Unwilling or Unable Doctrine and Self-Defense against Non-State Armed Groups

The matter may also be considered from the perspective of Syria, in whose territory the attack took place, and which State was deemed by the US as “unwilling or unable to prevent the use of its territory by non-State militia groups responsible for [the attack.]”

Unlike the UN framework for the crime of aggression, which requires State attribution, the Charter is silent on the source of the attack in self-defense, i.e. whether the right in Article 51 can only be triggered by an armed attack attributable to a State, or whether an armed attack by a non-State actor, without the involvement of a State, can also be subject of self-defense.

There is, of course, no question that a non-state armed group can be capable of executing an armed attack that can threaten the territorial integrity or political sovereignty of a State; the issue is whether a State can respond in self-defense using force in response to such an attack, especially when the non-State armed group is conducting the attack from or within the territory of another State, which has no involvement in the attack, nor has control or direction of the non-state actors.

In such cases, the US has applied the “unwilling or unable” doctrine as a way of resolving the possible conflict of sovereignty that may arise as a result of a military intervention. That is, where the territorial State, given a reasonable opportunity to do so, is deemed unwilling or unable to address an armed attack or threat of an attack against another State, which threat emanates from a non-State actor located in its territory, though not under its control nor direction, the target State can resort to the use of force in self-defense against such non-State actor in the territorial State. The inability or unwillingness of the State to suppress the attack would preclude wrongfulness in the use of force on the part of the target State. It has been argued that the basis for the doctrine’s application is the neutrality doctrine, the principle of necessity in jus ad bellum, and the general obligation of States to ensure that their territory is not used to wage attacks against other States.

The US cited the doctrine in its war against Al-Qaeda and the Taliban to justify military operations outside Afghanistan (e.g. military operation on Osama bin Laden in Pakistan), which were without the consent of the territorial State. In its February 2021 military action in Syria, the US relied on the doctrine as basis to conduct the strike in Syrian territory, even though the attacks against it took place in Iraq and despite information that the non-state armed militia responsible for the attack were supported by Iran.

There are a number of non-state armed groups located or operating in the Philippines, of varying degrees and manner of armed confrontations with the State. These include the New People’s Army (NPA) of the Communist Party of the Philippines (CPP), the Moro National Liberation Front (MNLF), the Moro Islamic Liberation Front (MILF), the Bangsamoro Islamic Freedom Fighters (BIFF), Islamic State (IS) East Asia, ISIS Philippines, Daulah Islamiyah, the Maute Group and the Abu Sayyaf Group (ASG). The list might not be exhaustive in view of the known presence of other armed elements with fluid or unstable membership and affiliations.

There has been no claim that any of these groups act as proxies for, or are backed by, the State in their violent activities. Not all are engaged in what would qualify as non-international armed conflicts (NIACs) with the Philippine State. The Government entered into peace agreements with the MNLF and the MILF and, until recently, was in peace negotiations with the CPP-National Democratic Front (NDF). In December 2020, the Philippines’ Anti-Terrorism Council designated the CPP-NPA, along with IS-East Asia, Daulah Islamiyah and the Maute Group as terrorist organizations under the Philippines’ Anti-Terrorism Act of 2020. The ASG, CPP-NPA and ISIS Philippines have also been designated by the US as foreign terrorist organizations.

Under the unwilling or unable doctrine, should any non-State armed group located or operating in the Philippines, whether by itself, through, or in association with foreign criminal elements, pose a threat or conduct an armed attack against any other State, such a scenario can potentially put the Philippines at risk of an armed intervention from the target State, if the Philippines were deemed either unwilling or unable to prevent such attack or future attacks being planned within its territory. Said armed response from the target State may also come in the form of a covert military operation.

The likelihood of cyber attacks being waged against other States by non-State actors within our territory must also not be discounted. Rule 71 of Tallinn 2.0, a non-binding compilation of international law that applies to cyber operations, recognizes that at least per State practice, cyber operations conducted by non-State actors against a State which rise to the level of an armed attack given its ‘scale and effects’ may trigger self-defense under Article 51. Where such operations are launched in the territory of another State, use of defensive force in the latter’s territory is deemed “permissible” when it “complies with the principle of necessity, is the only effective means of defense against the armed attack, and the territorial State is unable or unwilling to take effective actions to repress the cyber armed attack.” Tallinn 2.0 notes that lack of expertise or technology needed to thwart a cyber armed attack can be construed as inability.

Thus, the possibility of non-state actors launching cyber attacks from within Philippine territory increases its vulnerability to defensive armed intervention from other States. This also stresses the importance of enhancing national capabilities for detecting and suppressing cyber operations of such nature within our midst.

The application of the unable or unwilling doctrine poses national security concerns for the Philippines, as it may arise in the context of non-state armed actors present or operating in Philippine territory, whether in land, cyber or even the maritime domain.

On one hand, the Philippines would not want its territory to be so vulnerable to military strikes from other States, depending on the latter’s assessment of the Philippines’ ability or willingness to address non-state armed threats in its territory. In cases where such non-state armed actors may not have committed offenses or crimes under domestic law nor pose any threat to the Philippines, it may also not be acceptable for the Philippines to act as proxy enforcer of foreign laws or foreign interests in its own territory. On the other hand, it is not desirable for the Philippines to seemingly offer a safe haven to terrorists or other armed elements posing threats to other States, or a venue for them to wage or plan attacks on other States.

As far as the US is concerned, the prospect of an armed intervention in the Philippines on the basis of the unwilling or unable doctrine does not seem likely. The doctrine requires that the territorial State be given a reasonable opportunity to address the threat. This requirement is complemented by the mechanism in the PH-US Mutual Defense Treaty (MDT) allowing the parties to consult with the other when its “territorial integrity, political independence or security is threatened by external armed attack in the Pacific.” Where such armed attack originates from within Philippine territory, the MDT provides both an obligation and an opportunity for the US to request assistance from the Philippines in addressing the threat and the Philippines is also obligated by treaty to extend such assistance, “in accordance with its constitutional processes.”

Aside from the US, other States have also either endorsed the doctrine, whether explicitly or implicitly, or have at least been ambiguous about it; a few States have also objected to its application. (Read here for a preliminary listing of the positions of States on the unwilling or unable doctrine.)


These issues are far from settled as some States, such as Austria, have raised concerns about the increasing number of unilateral instances of use of force inconsistent with the Charter and called for discussions at the UN level to revisit the parameters for self-defense.

The debate has not been limited to US allies or European countries either, as other States, like ASEAN neighbor and close bilateral partner, Indonesia, have taken the view that unilateral use of force against non-State actors in the territory of another State (not in control of the non-State actors) would be equivalent to an act of aggression.

India, China and Vietnam also weighed in on the subject of cross-border use of force in self-defense against non-state armed actors in the territories of non-consenting States (especially in the context of counterterrorism) during an Arria-formula meeting of the UN Security Council on the subject, which was hosted by Mexico on February 24. (The Chair’s Summary of the proceedings, released by Mexico on March 24, can be accessed here.)

In her remarks at the meeting, Professor Naz Modirzadeh of the Harvard Law School Program on International Law and Armed Conflict noted the “unsatisfactory” silence of a vast majority of UN Member States in the application and interpretation of the law of self-defense, despite the stakes involved:

“To effectively maintain international peace and security, all States should address the [question of self-defense] as a matter of priority. Not participating in these debates comes with a cost. Intentional or otherwise, States’ silence contributes to normative uncertainty… Silence might function, legitimately or not, as a kind of tacit support for particular claims in the law of self-defense. All Member States should be aware of the potential effect of silence when [they] deliberate on whether to weigh in or remain in the sidelines…”

Indeed, issues in use of force and self-defense are very much alive in the normative agenda of multilateral institutions. Not all of international law is reflected in treaty law, and on this issue, it can be expected that any emerging consensus would be drawn along the lines of State practice. Given the array of Philippine security interests involved, the informed participation of the Philippines in these debates, whether in the UN or elsewhere, and its active contribution to the corpus of State practice would be crucial for its national security.


The author is an alumna of the University of the Philippines where she received her bachelor of arts (magna cum laude) and Juris Doctor degrees. She received her LLM in National Security Law as a Fulbright Scholar from the Georgetown University in Washington DC, where she was also awarded the Dorothy Mayer Prize for Outstanding Academic Performance in 2017.

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