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  • Print publication year: 2018
  • Online publication date: April 2019

2 - Sources of international law



Law-making is not a straightforward process in international law. There is no centralised structure or global government responsible for identifying certain policy directions and legislating accordingly. With the exception of decisions of the United Nations (UN) Security Council and the European Commission, States have not agreed to being bound by resolutions or decisions of international organisations. International organisations and groupings of States like the UN General Assembly are no more capable of creating formal and binding legal norms than diplomatic conferences that discuss and draft agreements for signature and ratification by States. The most crucial difference between international law and domestic law is that, by and large, international law is created by the very subjects it binds – that is, States – without a formalised structure of government or legislature. This chapter focuses on the various law-making processes and structures available for creating international law. It first considers the traditional sources of international law as set out in art 38(1) of the Statute of the International Court of Justice (ICJ Statute) generally and the concept of hierarchy of norms and relative norms before considering each of the art 38(1) sources in turn. The chapter concludes by considering alternative sources of international law not covered by art 38(1): ‘soft law’ including that created by non-State actors, and the role of the UN in creating international law.

The traditional sources of international law

The cornerstone of any discussion relating to the sources of public international law is art 38(1) of the ICJ Statute. It provides:

1. The Court, whose function is to decide in accordance with international law such disputes as are submitted to it, shall apply:

  • a. international conventions, whether general or particular, establishing rules expressly recognized by the contesting states;

  • b. international custom, as evidence of a general practice accepted as law;

  • c. the general principles of law recognized by civilized nations;

  • d. subject to the provisions of Article 59, judicial decisions and the teachings of the most highly qualified publicists of the various nations, as subsidiary means for the determination of rules of law.

  • Article 38(1) clearly states where international law is to be found for the purposes of proceedings before the International Court of Justice (ICJ) and although only a handful of cases come before the ICJ each year, the jurisprudence of the Court holds great weight with the international legal community.

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    Alvarez, Jose, International Organizations as Law-Makers, Oxford University Press, Oxford, 2005
    Boyle, Alan and Chinkin, Christine, The Making of International Law, Oxford University Press, Oxford, 2007
    Koskenniemi, Martti (ed), Sources of International Law, Ashgate, Aldershot, 2000
    Verdier, Pierre-Hughes and Voeten, Erik, ‘Precedent, Compliance, and Change in Customary International Law: An Explanatory Theory’ (2014) 108 American Journal of International Law 389
    Zimmermann, Andreas, Oellers-Frahm, Karin, Tomuschat, Christian and Tams, Christian J. (eds), The Statute of the International Court of Justice: A Commentary, Oxford University Press, Oxford, 2012