Against the backdrop of the inconclusiveness of Conclusion 4(2) regarding the role of international organisations in the formation of custom, this chapter elaborates on the reasons behind this lack of consensus and how this has affected the end-product of the International Law Commission’s work; that is the Conclusions incorporated in the International Law Commission’s 2018 Report. Such an enquiry is, according to this chapter, the key to addressing the shortcomings of the International Law Commission’s approach and to understanding whether the relevant Conclusion bears a strong normative claim to hardening into lex lata.

In 1995, the 26th International Conference of the Red Cross and Red Crescent mandated the International Committee of the Red Cross to prepare a ‘report on customary rules of international humanitarian law applicable in international and non-international armed conflicts’. The Study on customary international humanitarian law, published in 2005, identified 161 rules of customary international humanitarian law and presented the material collected in their determination. Complemented by regular updates of its practice part, the Study has also been accessible online via the International Committee of the Red Cross’s customary international humanitarian law database since 2010. For the Study, the International Committee of the Red Cross needed to consider many of the methodological questions that the International Law Commission faced in its work on the identification of customary international law. Like the International Law Commission’s Conclusions on that topic adopted on second reading in 2018, the Study is based on the fundamental requirement of two elements: a general practice that is accepted as law (opinio juris). Among the issues arising from this approach, there were the questions whose practice it is that forms rules of customary international law and whether actors other than States could be relevant in this context.

As the International Law Commission’s Conclusion 13 on the identification of customary international law provides, decisions of international tribunals can be considered a subsidiary means for the ascertainment of rules of customary international law. As this chapter argues, the real contributors appear to be the claimants who raise and shape the discussions about customary international law before a tribunal, which decides only on the basis of the pleadings and observations submitted by the parties. In that sense, investors have emerged as the most powerful claimants who certainly influence the clarification of rules of customary international law through investor–State dispute settlement.This chapter thus argues that investors exercise a significant influence over the tribunals’ rulings; and addresses the contribution of investors through the combination of two concepts – namely, ‘framing’ and ‘spilling-over effect’. The chapter unpacks both arguments through the study of the exceptions to the local remedies rule by examining the lex lata customary international law of diplomatic protection and emerging interpretations in investor–State dispute settlement, with a special focus on the ‘futility exception’ to the exhaustion of local remedies.

The chapter presents and critically assesses the view on non-State actors expressed in the Conclusions on Identification of Customary International Law adopted by the United Nations International Law Commission in 2018. Conclusion 4(3), setting the requirement of practice, stipulates that ‘conduct of other actors is not practice that contributes to the formation, or expression, of rules of customary international law, but may be relevant when assessing the practice referred to in paragraphs 1 and 2’ (i.e. practice of States and international organizations). Conclusion 9, dealing with the requirement of opinio juris, does not mention non-State actors at all. The chapter first traces the history of the conclusions in the International Law Commission work and then casts some doubt on the position that the International Law Commission has adopted in light of the views of other actors. It shows that the International Law Commission fails to do justice to the complex relationship that nowadays exists between non-State actors and customary international law.

decommissioning; Royal Ulster Constabulary; DavidTrimble; Holy Cross School; Ian Paisley; John Hume;Tony Blair

The chapter offers a constructivist account of the burgeoning roles non-governmental organisations have assumed in the making of customary international law. While most of these roles are informal, and their influence on the content and interpretation of customary international law norms has been primarily indirect, non-governmental organisations do contribute to the formation of customary international law through an increasingly diverse set of activities. Non-governmental organisation documentation, litigation, lobbying, and other forms of advocacy have contributed to treaty-making and ratification; to the domestication and internalisation of international norms and processes, including domestic accountability and remedies; and to codifying the obligations of, and stimulating practice by non-State actors such as business and armed groups. Despite a broad acknowledgement of the increasing involvement of non-governmental organisations in global governance by scholars and practitioners, their role in customary international lawmaking remains under-appreciated. To understand the increased influence of non-governmental organisations on the identification, formation, and application of customary international law rules, the chapter offers a differentiated, effects-based account of non-governmental organisation participation in customary international lawmaking.

peace process; republicanism; loyalism; UlsterUnionism; defeat thesis; stalemate;pan-nationalism

The International Law Commission’s Conclusions on the identification of customary international law show that contemporary international law grant a modest role to international organisations as independent actors in the formation of customary international law, which is remarkable, given that organisations participate ever more fully in international legal affairs. One of the reasons for such a restrictive approach lies in the hesitation of the Commission to ascribe to international organisations a ‘juridical will’. In this chapter, this term is a shorthand for the various subjective, intentional states that systems of law project onto legal participants in order to operationalise legal agency. It shows that international law can accomodate States in this respect, but remains adverse to international organisations. This can be explained through the organisation’s functional and mechanical identity in international law, which has persisted even after organisations emerged as prominent independent legal actors. It is submitted that this is one reason why the ascertainment of an organisation’s opinio juris, or of an organisation’s distinct will in the attribution of practice, may pose a challenge. The chapter proposes that, in light of their current role in global affairs, international organisations assume a role in the formation of custom insofar as this is substantively relevant for their work, and that organisations be understood as the receptacle of a juridical will.

This chapter proposes a theoretical framework for the role of international organizations in the formation of customary international law that rejects their traditional conceptualization as double-faced entities. Under this paradigm, organizations are either considered as fora for the development of the practice and the opinio juris of States, or as independent actors that autonomously contribute to the formation of customary international law. The aim of the chapter is to describe an alternative framework to reconcile these two faces of the same coin. It will be shown that one approach does not exclude the other, and the adoption of one perspective is only motivated by specific purposes that do not rule out the relevance of the other view. The chapter first describes the either/or paradigm in order to read the work of the International Law Commission and of the International Court of Justice. Later, it describes three ‘anomalies’ of this paradigm that concern the development of so-called ‘objective regimes’ (section 3). Finally, section 4 builds a theoretical framework on the role of international organizations in the formation of customary international law that acknowledges their dual (and not double) nature.