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Havana Syndrome: An Armed Attack Under the UN Charter?

About the author: Aaditya Dixit is an external contributor to Travaux.

"United Nations" by Ashitaka San available here.


A mysterious ailment has recently affected several United States (US) diplomats. Intelligence agencies suspect that this is a targeted attack involving microwave-radiation weapons. Unfortunately, this is only the latest in a series of events that began to unfold in December 2016. Since then, several US spies have experienced similar symptoms, including dizziness, numbness, and a loss of motor control. Appearing first in Cuba, officials have dubbed this phenomenon “Havana Syndrome,” and hypothesized that it is caused by a microwave gun.

If these cases of Havana Syndrome are concerted attacks attributable to a State or non-State actor, it is important to determine whether Article 51 of the UN Charter entitles the US to invoke self-defense. This inquiry raises two questions of international law. First, can unconventional weapons perpetrate an “armed attack” as defined by Article 51 of the UN Charter? Second, does the use of microwave-radiation weapons against individuals constitute an armed attack?

Defining “Armed Attack”

Article 51 of the Charter recognizes States’ “inherent right of individual or collective self-defense” if they are subjected to “an armed attack.”. Although the Charter does not define “armed attack,” the term is widely recognized as more than the mere “use of force.” According to Dapo Akande and Antonios Tzanakopoulos, legal scholars at Oxford University, the distinction between a use of force and an armed attack is the degree or gravity of force employed. The International Court of Justice (ICJ) has made a similar distinction. In its 1986 Nicaragua v. United States of America ruling, the ICJ held that armed attacks are “the most grave forms of the use of force.” The ICJ reiterated this distinction in its 2003 Case Concerning Oil Platforms opinion.

Some events are clearly armed attacks. In 1974, the UN General Assembly adopted Resolution 3314, with the Definition of Aggression annexed. The Definition recognizes that “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” constitutes an act of aggression. In Nicaragua, the ICJ wrote that the Definition reflected “customary international law.” While not all forms of aggression amount to an armed attack (e.g., occupying a country), aggression and armed attacks are closely linked, and the difference between them is often overlooked.

Although the resolution identifies other acts which are recognized as armed attacks, they do not articulate a precise definition. Bruno Simma’s The Charter of the United Nations: A Commentary provides a more concrete definition, defining an armed attack as “force used on a relatively large scale” with “sufficient gravity” that leaves a “substantial effect.” While still broad, Simma’s definition provides some identifiable boundaries. Simma asserts that “force” under the Charter only extends to armed force, noting that the Charter’s drafters rejected attempts at including other forms of coercion in the definition of force.

Can Electronic Weapons Be Used to Perpetrate an Armed Attack?

Although the Charter has a limited definition of force, it contemplates evolving weapons technology and the role of such technology in perpetrating armed attacks. The ICJ confirmed this in its 1996 Legality of the Threat or Use of Nuclear Weapons opinion, noting that the “provisions [of the Charter] do not refer to specific weapons. They apply to any use of force, regardless of the weapons employed.” Further, according to Yoram Dinstein, armed attacks can be perpetrated by weapons that do not use kinetic force. Therefore, electronic weapons could conceivably be used to perpetrate an armed attack. Nonetheless, the act of aggression must fulfill the gravity requirement. For instance, Rule 71 of the Tallinn Manual 2.0 recognizes that a cyber-attack can amount to an armed attack when “an act that seriously injures or kills a number of persons or that causes significant damage to, or destruction of, property would satisfy the scale and effects requirement” of an armed attack.

Would the Use of Microwave-Radiation Weapons on Individuals Satisfy the Definition of an Armed Attack?

Multiple prior acts of violence demonstrate that an attack on a prominent individual or a small group can also amount to an armed attack. For example, the assassination attempt on George H.W. Bush motivated several States to support the US’s right to invoke Article 51. Subsequently, during the 2006 Israel-Lebanon conflict, the Security Council Debates revealed support for Israel invoking Article 51 after its border patrol unit was attacked. Additionally, scholars recognize that “an armed attack may also include, in certain circumstances, attacks against private citizens abroad.”

Although the individual attacks on US diplomats may not be grave enough to justify the invocation of self-defense, a gravity analysis may apply to the sum of the harm rather than to the harm resulting from each attack. Under the accumulation of events doctrine, individual attacks can be aggregated to constitute an armed attack even though they cannot cross the gravity threshold individually. Since the Charter is not a suicide pact, it would be unreasonable to expect States to repeatedly suffer attacks and not respond. Past practices of the US, UK, and Israel support this notion, and the ICJ’s discussion in Oil Platforms suggests that aggregating individual attacks could satisfy the gravity requirement to constitute an armed attack.

The US Can Likely Invoke Article 51

The concepts of force and armed attacks have evolved significantly in practice, judicial opinions, and scholarship. The ICJ’s treatment of force and armed attacks shows that these concepts must not be confined by rigid definitions or semantics. The accumulation of events doctrine, combined with precedent showing that cyber attacks can constitute uses of force, suggest that the recent attacks on US diplomats meet the Charter’s definition of an armed attack. Therefore, Article 51 of the Charter may permit the US to initiate a legitimate defensive response of the perpetrator of these attacks, especially if the number of cases continues to rise.

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