Over the last two decades, international humanitarian law (IHL) has seen a stalling with regard to States’ willingness to adopt treaties or to be formally involved in the development of IHL. This raises the question of whether holding on to the doctrine of sources as laid down in Article 38 of the Statute of the International Court of Justice is the only way to meaningfully further develop IHL. Indeed, in recent years IHL instruments have often dispensed with certain formalities that are traditionally linked to (the formal sources of) international law; this phenomenon is also called “informal international law-making” (IIL). The present contribution will analyze IIL as an alternative way forward in light of the current “deadlock” caused by States’ unwillingness to conclude new IHL treaties or to recognize customary IHL. In this article, we will investigate and assess the opportunities, shortcomings and pitfalls offered by informality by looking into examples of IIL within IHL. More concretely, we will look into State practice in relation to (1) the Safe Schools Declaration, (2) the Tallinn Manual and Tallinn Manual 2.0, and (3) the Montreux Document. Most importantly, our findings will assess whether IIL can overcome one of its alleged main disadvantages: its lack of effectiveness.

Armed reprisals are the limited use of military force in response to unlawful actions perpetrated against states. Historically, reprisals provided a military remedy for states that had been wronged (often violently) by another state without having to resort to all-out war in order to counter or deter such wrongful actions. While reprisals are broadly believed to have been outlawed by the UN Charter, states continue to routinely undertake such self-help measures. As part of the roundtable, “The Ethics of Limited Strikes,” this essay examines the doctrine of armed reprisals in light of recent instances of states using force “short of war” in this manner. We argue that the ban on reprisals has been largely ignored by states, and that recent attempts to apply the laws of armed conflict to the cyber domain (such as the Tallinn Manual) are further weakening this prohibition. We conclude that this is a potentially dangerous development that lowers the bar for resorting to military force, risking escalation and thereby further destabilizing the international system.

Why do we need dialogue between ethical and legal perspectives on norms governing the initiation and conduct of interstate conflict? This essay will examine this question by first critiquing the 2013 Tallinn Manual on the International Law Applicable to Cyber Warfare, which sought to apply existing legal frameworks that govern international violence to a new form of conflict. While the manual is for the most part ethically commendable, the first half of the essay will highlight several of its ethical shortcomings and will then extract general reasons why international law nevertheless must be informed by ethical analysis. The second part of the essay will affirm the importance of law for ethical analyses of justified responses to the burgeoning phenomenon of sublethal harms. While states have always used sublethal harms to weaken adversaries, technological developments have magnified the regularity and effectiveness of these practices, particularly against free societies. Responses to such attacks may include—in addition to defensive countermeasures—punishments that deter and reform, and may target “indirect participants” such as financial supporters. However, determining which responses are ethically justified will require insights gleaned from criminal and tort law.

How should international law deal with the uncertainty arising from the rise of irregular forms of warfare? In the past decade, this question has been the topic of several reports produced by international groups of experts in the field of conflict and security law. The most recent examples include the study on the notion of the ‘direct participation in hostilities’ under the auspices of the International Committee of the Red Cross, and the Tallinn Manual on cyberwarfare prepared at the invitation of NATO. In this article, we discuss the Tallinn Manual, showing how experts faced with uncertainty as to the law's precise scope and meaning construct legal interpretations, legal definitions, and institutional facts and norms that can be used to make sense of a contingent world. At the same time, we argue, this absorption of uncertainty produces new uncertainty. Consequently, the power of experts does not reside in their knowledge, but in their control and management of uncertainty and non-knowledge.