One of the most important responsibilities for a military commander is the protection of his or her own troops. Military personnel are informed that they have a right, and even an obligation, to use force to defend themselves and their units against attack or imminent attack. This right, often called "unit self-defense," is recognized by militaries around the world and serves as a key element of militaries' Rules of Engagement (ROE). (1)
A significant amount of legal scholarship has focused on the meaning of national self-defense under international law, particularly following the September 11 attacks and the 2003 U.S. invasion of Iraq. Legal scholars, practitioners, and international courts have parsed the meaning of "armed attack," (2) argued over the legitimacy of anticipatory self-defense, (3) and debated application of the Caroline doctrine (4) in states that are unwilling or unable to prevent armed attacks by non-state actors. (5)These articles generally focus on when and how states can use force against another state, or within the territory of another state, in self-defense. Yet there has been little attention to when soldiers can use force under international law to defend themselves against attacks or threatened attacks.
In particular, the source and scope of the right of unit self-defense has not been carefully examined in academic literature. Military ROEs assert the right of unit self-defense and numerous articles presuppose that such a right exists--it seems intuitive that this must be the case. Yet there is no clear source for this right as it is not codified in any international convention or treaty. Perhaps for this reason, several scholars have stated that the right of unit self-defense must be a subset of the right of national self-defense reflected in Article 51 of the United Nations Charter. (6) But, as this Article argues, the right of unit self-defense does not fit comfortably within the national self-defense framework.
This is the first thorough examination of the jurisprudential basis for unit self-defense in military Rules of Engagement under international law. (7) This Article argues that the right of unit self-defense is derived from customary international law and that it must be separate and distinct from the right of national self-defense. This is not a purely academic distinction, as states are required to report all actions taken in national self-defense to the U.N. Security Council. Moreover, maintaining a distinction between unit and national self-defense would mitigate concerns generated by the International Court of Justice's (ICJ) conservative interpretation of the right of national self-defense under Article 51 of the U.N. Charter.
Part I of this Article describes the concept of unit self-defense, drawing on various countries' Rules of Engagement. Part II critiques the arguments that unit self-defense is a subset of national self-defense, noting key differences regarding when and how these rights can be exercised. Part III explains that unit self-defense, although not derived from Article 51, is nevertheless recognized under customary international law, as evidenced by state practice and opinio juris. Part IV argues that understanding unit self-defense as an independent right can help make sense of several of the perceived inconsistencies in the ICJ's jurisprudence on self-defense, most notably in the Case Concerning Military and Paramilitary Activities in and Against Nicaragua. (8) Part V discusses the similarities between individual and unit self-defense, and raises some additional questions that warrant further attention in the academic literature.
I. AN OVERVIEW OF UNIT SELF-DEFENSE
The right of unit self-defense is "fundamental to all international military codes" and Rules of Engagement. (9) It "allows a commander, or an individual soldier, sailor or airman the automatic authority to defend his or her unit, or him Or herself, in certain well defined circumstances." (10) United States' military doctrine has traditionally defined "unit self-defense" as follows: "The act of defending a particular US force element, including individual personnel thereof, and other US forces in the vicinity, against a hostile act or demonstrated hostile intent." (11)
Unit self-defense is "an inherent right and not dependent or contingent on a mandate or mission." (12) In the United States military, unit self-defense is considered both a "right and obligation." (13) This right extends to the entire unit, regardless of its nature, which in this context can consist of "an army platoon, a ship, an aircraft, or can encompass a national or international task force which is operating as a single unit." (14) In most circumstances, however, it does not apply to the protection of non-military personnel and property or to foreign forces. (15)
Pursuant to the SROE, unit commanders "always retain the inherent right and obligation to exercise unit self-defense in response to a hostile act or demonstrated hostile intent." (16) A "hostile act" generally refers to "an attack," while "hostile intent" means the "threat of imminent attack" (17) and is "manifested by actions which are immediately preparatory to that armed attack." (18) According to the United States Commander's Handbook on the Law of Naval Operations ("Commander's Handbook"), "[t]he determination of whether or not an attack is imminent will be based on an assessment of all facts and circumstances known to U.S. forces at the time and may be made at any level." (19) This determination, often made "in a dynamic operational context on the basis of incomplete and often conflicting information," is one of the more difficult decisions for a commander. (20)
After unit self-defense is triggered, the use of force may be exercised "so long as the hostile act or hostile intent continues." (21) In all circumstances, the use of force must be both necessary and proportional to the underlying threat or attack. (22) In many national ROEs, "[d]eadly force is to be used only when all lesser means have failed or cannot be reasonably employed." (23) If the situation permits, potentially hostile forces should be warned and given the opportunity to withdraw before deadly force is employed. (24)
Consider how unit self-defense might apply in the following hypothetical scenarios. In the first, Troy has a small Air Force base located in Atlantis, even though the countries have a tense relationship at times. One day, a mob of Atlantean citizens gathers around the main gate to the base and hurls rotten fruit and stones inside the base's perimeter. As tensions grow, a few unruly Atlanteans launch Molotov cocktails at the base guards, injuring several of them. The base commander calls for the Atlantis police to break up the mob, but they are slow to respond. As the violence escalates, Trojan guards fire tear gas into the crowd and detain individuals caught holding cans of gasoline.
In the second scenario, Macedonia has requested the assistance of Sparta to help defend itself against armed groups operating in Macedonian territory. Macedonia and Sparta sign a treaty stating that all of Sparta's military operations will be coordinated with Macedonian authorities, except in cases of self-defense. On several occasions, armed groups attack Spartan patrols. Sparta has intelligence that the leaders of these attacks are meeting in an abandoned warehouse. Spartan authorities are in a position to destroy the building but do not have time to coordinate the mission with Macedonia's authorities.
In the first example, it is clear that the Troy military guards would have the right to use force to defend themselves against the aggressive acts committed by Atlantean civilians. Throwing Molotov cocktails constitutes a clear "hostile act," triggering the right of unit self-defense. This right would in some circumstances include the authority to temporarily detain the attackers, pending their transfer to Trojan law enforcement authorities. (25) The second example is more complicated. Although the Spartan forces have intelligence that the perpetrators of prior attacks are located in a warehouse, there is no indication that these terrorists are preparing an imminent attack against Spartan units. Accordingly, Spartan forces could not likely rely on the self-defense exception to the treaty requirement that all military actions be coordinated with the Macedonian authorities.
II. UNIT SELF-DEFENSE: A SUBSET OF NATIONAL SELF-DEFENSE?
The right of unit self-defense is widely asserted by militaries around the world, yet its source has been examined only cursorily. The most common argument in academic literature is that unit self-defense is derived from the inherent right of national self-defense recognized by Article 51 of the U.N. Charter. (26) This Part examines those arguments and ultimately finds them unpersuasive.
A. Arguments that Unit Self-Defense is a Subset of National Self-Defense
Yoram Dinstein, a preeminent scholar on the law of war, argues that unit self-defense--which he refers to as "on the spot reaction"--is a subset of national self-defense. (27) He states that "[t]here is a quantitative but no qualitative difference between a single unit responding to an armed attack and the entire military structure doing so." (28) According to Dinstein, self-defense is always exercised by the state; the actions of the lowest-ranking soldier and the highest-ranking general are attributed to the state that put them in charge. He concludes: "Once counter-force of whatever scale is employed by military units of whatever size--in response to an armed attack by another State--that is a manifestation of national self-defence, and the legitimacy of the action is determined by Article 51 as well as by customary international law." (29)
Hans Hosang similarly argues that the "right to unit self-defence is primarily derived from the right of national self-defence." (60) He explains that "military units [are] representatives of the sovereign State to which they belong" and thus share the "sovereign rights enjoyed by the State." (31) Although Hosang acknowledges some important differences between national and unit self-defense, he argues that these differences can be "addressed by viewing unit self-defence as a tactical level right, whereas the right of national self-defence is a strategic level right." (32) Other commentators have similarly stated that "[t]he most relevant and applicable view of [unit] self-defense in international law resides in Article 51 of the U.N. Charter." (33)
B. Criticisms of the National Self-Defense Theory
There has been little critical analysis of the theory that unit self-defense is a manifestation of the right of national self-defense. The lack of analysis is surprising given the implications that such a theory would have for states, including the obligation to report actions taken in national self-defense to the Security Council and for how states characterize unit self-defense in treaty practice. This Section examines the weaknesses in the national self-defense theory and argues that it is unsustainable.
First, it is inconsistent with what many states say and do. The 2000 SROE, for example, state: "The exercise of the right and obligation of national self defense by competent authority is separate from and in no way limits the commander's right and obligation to exercise unit self-defense." (34) The San Remo Handbook on Rules of Engagement, which was drafted by experts from several military powers, also recognizes the distinction between unit and national self-defense. (35) The Israeli Turkel Commission similarly endorsed this distinction, stating that "[f]rom a doctrinal perspective, the right [of self-defense] is often divided into individual, unit, and national self-defense." (36)
Second, it blurs the legal personality of the nation and the individual (or unit of individuals). The U.N. Charter regulates inter-state conduct and does not speak to individuals' right to defend themselves (as opposed to their nation) against an attack or imminent attack. (37) The Rome Statute, which established the International Criminal Court, makes this distinction clear. Article 31(1) states that a person shall not be held criminally liable for conduct if "[t]he person acts reasonably to defend himself or herself or another person ... against an imminent and unlawful use of force in a manner proportionate to the degree of danger to the person or the other person or property protected." (38) The second sentence in Article 31(1)(c) recognizes the dual nature of self-defense. It states: "The fact that the person was involved in a defensive operation conducted by forces shall not in itself constitute a ground for excluding criminal responsibility under this subparagraph." (39) In other words, the fact that a soldier uses force under a national self-defense theory does not necessarily exclude him from criminal liability for acts taken in his "official capacity as agent of a collective entity, like a State." (40) Rather, the "exclusion …