Just as old as the dispute over the coercive protection of nationals abroad is the dispute over preventive self-defence. When Britain and the United States had a dispute in 1837 over a British raid on the steamship Caroline on American territory, the two colleagues agreed that it was permissible to violently prevent an armed attack if it was imminent. The Nuremberg Military Tribunal was to confirm this famous Caroline precedent in 1946. Almost at the same time, however, a dispute arose over whether the Charter of the United Nations had abolished this ancient right to limited preventive self-defence. Again, opponents of this view argued that Article 51 of the Charter of the United Nations did not affect the customary right to self-defence prior to the Charter. In the meantime, the same result has been justified by arguing that the reference to armed attacks in article 51 leaves room for the inclusion of imminent armed attacks. However, the wording of that provision does not provide any approximate and unequivocal support for that interpretation. For this reason alone, it is not surprising that the dispute over pre-emptive self-defence continues. History offers a relatively small sample of cases to provide clues to these issues; States simply do not beat their counterparts too often in the name of self-defence. When they do, experts and politicians often spend years debating the claimed justifications. Due to the lack of justification of jus ad bellum, the 2017 and 2018 attacks on forces loyal to the regime remain contrary to international law. In recent years, the question of whether violating the prohibition of violence requires a certain intensity of adverse effects has been much greater than before. States do not systematically condemn minimally invasive violations of territorial sovereignty such as the use of force.
Although the abduction of Eichmann by Israeli intelligence in Argentina may remain a unique case, the evacuation of its own nationals from a situation of non-international armed conflict abroad remains a recurring occurrence in State practice. The question of whether and under what conditions such rescue operations constitute the use of force is not trivial. The use of force is more difficult to justify under international law than violent encroachment on foreign territorial sovereignty. In particular, the possibility of invoking the state of emergency as a legal justification is excluded in the case of coercive measures, but not in the case of other measures. In an evacuation like that of the German citizen of besieged Libya in 2011 (Operation Pegasus), this subtle difference could prove decisive. The German government justified the use of an air force aircraft with the tacit consent of the Libyan government, as the Libyan government had not responded to an earlier German request. This interpretation of the silence of the Libyan government, which at the time was apparently heavily occupied elsewhere, is beyond doubt. The German government took refuge in this somewhat shaky attempt at justification because Germany did not suffer any armed attack that would have justified the use of force in self-defense, and it was not clear that such an armed attack was imminent. Given the rapidly escalating conflict in Libya, however, there is a danger to life and physical integrity there, creating an emergency situation for Germany under international law. If the rapid evacuation of threatened nationals had remained below the threshold for the use of force because of its minimally invasive nature, the Federal Government would have had a plausible argument of necessity.
As things stand, evacuation was necessary to avoid the threat to the fundamental rights of individuals, and interference in Libya`s territorial sovereignty carried far less weight than the threat to those rights. Nevertheless, the federal government did not make any arguments of necessity – for example, because it wanted to avoid the legal assertion that the prohibition of violence is linked to a threshold of intensity. In this context, it should also be noted that the UK has described the nerve agent attack on Sergei and Yulia Skripal in Salisbury in March 2018 as an “unlawful use of force”. In international jurisprudence, the question of a de minimis threshold for Article 2, paragraph 4, of the Charter of the United Nations has recently become increasingly important. Nevertheless, the right of a state to defend itself (individual self-defence) or to defend another state at its request (collective self-defence) – as well as interventions by invitation – is at the heart of recent State practice. As with the prohibition of the use of force, a change in the direction of the discussion can also be observed in the field of international law for self-defence. For decades, the central question has been whether the right to self-defence is limited to the possibility of armed attack or whether certain violations of the law below this threshold can also be avoided by the use of force. It is not clear that states such as the United Kingdom, Israel and the United States – which had previously advocated for Article 51 of the UN Charter to recognize the broader version of the right of self-defence in accordance with customary international law before the Charter – would now commit to a narrower interpretation. However, it is not disputed that today`s States generally attach more importance to establishing a link to an armed attack when invoking the right of self-defence than in the first decades after 1945. This trend can certainly be seen as a consolidation of international peace and security law.
But it should not be forgotten that some old controversies are now continuing in the form of a dispute over the correct interpretation of the concept of armed attack. Specifically, there is uncertainty about the intensity threshold of an application of force, the type of attacker, and the target of the attack. Controversies over when the right to self-defense begins and ends are closely related to this. What standards does the international community use to determine its legitimacy? More convincing might be the idea that a government could lose its authority to call on foreign states to use force on its territory if it provoked the armed conflict by committing crimes against its own people under international law, or if it systematically committed war crimes during the armed conflict. However, the extremely uncertain international reaction to the Russian invitation to Syria, which was initiated in 2015 and lasted several years, shows that the international legal situation still awaits clarification. It is at least indisputable that the commission of genocide, crimes against humanity and war crimes with the direct participation of a government does not automatically entail the loss of government status under international law.