Second, although the incidents discussed above reveal a certain hesitation to invoke use-of-force language in the context of small-scale armed confrontations between states, several other incidents can be identified in which Article 2(4) or 51 was invoked. In relation to the previously mentioned shooting of an American military air transport within Yugoslav airspace in 1946 (because of bad weather), for instance, the United States argued that, since the plane in no way constituted a threat to the sovereignty of Yugoslavia, the actions were "a plain violation of the obligations ... under the Charter of the United Nations not to use force except in self-defense." (151) In a similar vein, in 1981, a confrontation between U.S. and Libyan military aircraft in the Gulf of Sidra (at a time when tension between the two states was high and the United States was conducting a military exercise off the Libyan coast) resulted in the downing of two Libyan aircraft. (152) In reaction, Libya complained before the Security Council that by "using force and direct threat" against it, the United States had committed an "act of aggression, thus violating the United Nations Charter and the principles of International Law." (153) By contrast, the United States asserted that it had acted in accordance with Article 51. (154) Similarly, when Pakistan brought proceedings before the ICJ after India allegedly downed a Pakistani military aircraft over Pakistani territory (resulting in sixteen deaths), it claimed that India had violated Article 2(4). (155) Along the same lines, states such as Iraq, Lebanon, and Libya have occasionally complained to the Security Council about recurrent incursions into their airspace and have explicitly asserted their right of self-defense. (156) In a February 2003 letter to the Security Council, for instance, Lebanon declared that "given that the Israeli violations of ... Lebanese airspace constitute unlawful acts of aggression and provocation, Lebanon will exercise its natural and lawful right of self-defence, opposing them with ground anti-aircraft fire." (157) Likewise, military doctrines often explicitly construe the use of force against intruding military vessels or aircraft by reference to the Charter rules on the use of force (in particular, the right of self-defense) rather than as a form of "law enforcement." The U.S. Commander's Handbook on the Law of Naval Operations, for instance, states that
[m]ilitary aircraft intruding into foreign airspace on a military mission may constitute a sufficient threat to justify the use of force in self-defense. This appears true both for tactical military aircraft capable of directly attacking the overflown state and for unarmed military aircraft capable of being used for intelligence-gathering purposes. (158) The Australian Operations Law for RAAF Commanders similarly states that "[t]here is no general right to attack an intruder, whether civil or military.... Thus an intruding aircraft may only be attacked where the right to invoke Article 51 self-defence can be demonstrated." (159)
Article 2(4) or 51 has also been invoked in relation to various naval incidents. One such case involved the sinking of the Israeli destroyer Eilat in United Arab Republic territorial waters in the aftermath of the 1967 Six-Day War. According to the UAR, the naval incursion constituted an aggressive act that was in flagrant violation of the Security Council's cease-fire resolution and that compelled UAR naval units to act in self-defense to stop the vessel's advance. (160) In the ensuing Security Council debates, some agreed that the UAR had acted in self-defense in the face of aggression, (161) although most states confined themselves to urging both parties to show restraint. (162) Again, in 1968, when North Korea seized the USS Pueblo, (163) the United States, claiming that the arrest took place in international waters, spoke of an "aggressive military action" in violation of the UN Charter (164) (a position supported by the United Kingdom). (165) In response, North Korea claimed that the vessel was caught spying in North Korean waters, and thus centered its justification on self-defense and security needs--a response to the United States' "open aggression" rather than on an exercise in law enforcement (166) (a position backed by the Soviet Union). (167) In the 1964 Gulf of Tunkin incident, the United States claimed that its military vessels had taken defensive action in reaction to deliberate attacks by North Vietnamese torpedo boats. (168) The United States' invocation of Article 51 (169) was explicitly supported by the United Kingdom, (170) though other states questioned the U.S. version of the facts and suggested that it had gone beyond mere on-the-spot defensive action. (171) Another example, also discussed earlier, was Sweden's 1982 use of depth charges and mines against a foreign (presumably Soviet) submarine near a top-secret Swedish naval base. A report by the Swedish Submarine Defence Commission concluded that the actions constituted lawful self-defense under Article 51. (172)
On a related note, while it does not constitute state practice, the recent case before the International Tribunal for the Law of the Sea concerning Ghana's detention of the Argentine frigate ARA Libertad merits attention. In its order imposing provisional measures, (173) the tribunal unequivocally affirmed the sovereign immunity of foreign warships, even when in the port or internal waters of another state, and ordered Ghana to release the frigate. The order itself does not explicitly mention the UN Charter provisions. It does, however, note in passing that "any act which prevents by force a warship from discharging its mission and duties is a source of conflict that may endanger friendly relations among States." (174) Interestingly, Judge Chandrasekhara Rao, in his separate opinion, noted with regret that the order failed to state clearly "that even an attempt to threaten or use of force against a warship would be a matter impinging on the maintenance of international peace and security." (175) In so doing, the judge quotes the following excerpt from Bernard Oxman:
An attempt to exercise law enforcement jurisdiction against a foreign warship is in fact an attempt to threaten or use force against a sovereign instrumentality of a foreign State. That is primarily the subject matter of the law regarding the maintenance of international peace and security, not the law of the sea as such .... (176) Last but not least, the language of self-defense and of UN Charter Article 51 is also regularly invoked in relation to small-scale confrontations between ground troops. In 1976, for example, China stated that a group of Indian troops had intruded into Tibet. (177) When the staff of a civilian checkpost told the troops to withdraw, they opened fire, whereupon the checkpost staff fired back. China claimed self-defense. In February 2007, Israel reported to the Security Council that its own soldiers, operating within Israeli territory, had been fired upon by the Lebanese army. According to Israel, returning fire was "entirely legitimate and in self-defence." (178) Yet another example concerns an armed incident between Cambodian and Thai troops in the area of the Temple of Preah Vihear in 2008. Thailand, for its part, considered
Cambodian soldiers' intrusion into Thailand's territory and their shooting at Thai soldiers a serious violation of Thailand's sovereignty and territorial integrity. Cambodia's provocation constitutes an act of aggression in blatant violation of international law. Thus, Thailand had no choice but to exercise the inherent right of self-defence, as provided for under the Article 51 of the [UN Charter]. (179) According to Cambodia, however, Thai troops had entered its territory and "fired guns on Cambodian soldiers, who had no choice but to exercise their right to self-defence in accordance with Article 51 of the [UN Charter]. As a consequence, two Cambodian soldiers were killed and two were injured." (180) And in 2006, Israel invoked Article 51 in response to what was Hezbollah's cross-border attack on an Israeli border patrol, during which two soldiers were captured and several were killed. (181) Although the resulting Israeli intervention in Lebanon was widely seen as disproportionate, it is noteworthy that--despite its small scale--most states did regard the original provocation as an armed attack under Article 51. (182) Even though the attack was carried out by a nonstate actor, the precedent illustrates that small-scale attacks can be sufficiently grave to constitute armed attacks and, by definition, grave enough to constitute a use of force. (183)
In light of the foregoing, it is reasonable to conclude that any actual armed confrontation between two states, even if small-scale or localized, comes within the ambit of the jus ad bellum. This author thus agrees with Dinstein that a state's enforcement of its territorial rights against an illegal incursion cannot be simply excluded from the scope of UN Charter Article 2(4). (184) Rather, whenever state A deliberately uses (potentially) lethal force within its own territory-including its territorial sea and its airspace--against military or police units of state B acting in their official capacity, that action by state A amounts to the interstate use of force in the sense of UN Charter Article 2(4). (185) It immediately follows that, in the context of armed confrontations between states, the application of Article 2(4) is not subject to any de minimis threshold.
What About Unlawful Territorial Incursions That Do Not Result in Actual Armed Confrontation? An Exercise in Reverse Engineering
A question nonetheless remains as to the extent that unlawful territorial incursions by military or police units (by land, sea, or air) that do not result in actual armed confrontations come within the scope of UN...