Introduction
The question of whether international law is ‘truly law’ is a classic and enduring debate in legal and political theory. Sceptics point to the absence of a global legislature, a system of courts with compulsory jurisdiction, and an overarching enforcement body, arguing that what we call international law is little more than a collection of moral or political norms. Proponents, however, argue that it is a unique but valid legal system that governs the relations between states. This essay will argue that while international law does not fit the typical model of a domestic legal system, it is nevertheless rightly considered law. It possesses its own sources, systems of interpretation, and mechanisms for compliance which, although different from those in national law, are recognised and relied upon by states. By examining the arguments from legal theory and the reality of state practice, it becomes clear that international law functions as a legal system in its own right.
The Challenge from Legal Positivism
The most famous critique of international law’s legal character comes from the 19th-century legal positivist, John Austin. For Austin, law is a species of command. Specifically, a law is a command issued by a sovereign, which is habitually obeyed by a population and which is backed by the threat of a sanction if it is disobeyed (Austin, 1832). When this definition is applied to the international sphere, international law appears to fail on every count.
First, there is no single, identifiable global sovereign. The international system is characterised by the sovereign equality of states; there is no single political superior with the authority to legislate for all nations. While the United Nations General Assembly can pass resolutions, these are generally not legally binding. Second, there is no consistent or reliable system of sanctions. While the UN Security Council is empowered under Chapter VII of the UN Charter to take enforcement action, including military action, its power is often neutralised by the political interests of its five permanent members (P5) and their power of veto. This has been seen in numerous crises where the Security Council has been unable to act decisively. Without a sovereign to issue commands and a reliable mechanism to enforce them, Austin concluded that international law was not law ‘properly so called’, but rather a form of ‘positive morality’ consisting of opinions or sentiments held by the international community (Austin, 1832). This view, which equates law with coercion, remains a powerful argument for those who are sceptical about the legal status of international law.
A More Modern Conception of Law
The Austinian critique, while influential, relies on a narrow definition of law that is modelled exclusively on a domestic criminal statute. A more sophisticated understanding of law was provided by H.L.A. Hart, who argued that Austin’s command theory was inadequate to explain even domestic law, let alone international law. Hart proposed that a legal system is best understood as a union of ‘primary’ and ‘secondary’ rules (Hart, 2012). Primary rules are those that impose duties or grant rights to individuals (or, in this context, states), such as the prohibition on the use of force. Secondary rules are rules about the primary rules; they specify how primary rules are created, changed, and adjudicated. Hart identified three types of secondary rules: a rule of recognition, rules of change, and rules of adjudication.
Applying Hart’s framework, international law appears more like a genuine legal system. It is rich in primary rules, such as the principles of territorial integrity, diplomatic immunity, and respect for human rights. The crucial question is whether it possesses secondary rules. Arguably, it does, albeit in a decentralised form. The ‘rule of recognition’ for international law can be found in Article 38(1) of the Statute of the International Court of Justice (ICJ). This article lists the sources of international law that the Court is to apply: international conventions (treaties), international custom, the general principles of law recognised by civilised nations, and, as subsidiary means, judicial decisions and the teachings of publicists. This provides a framework for identifying what counts as a rule of international law.
Similarly, there are ‘rules of change’. Treaties can be created, amended, and terminated according to established procedures, such as those set out in the Vienna Convention on the Law of Treaties 1969. Customary international law also evolves over time through the combination of state practice and opinio juris (a belief that the practice is required by law). Finally, ‘rules of adjudication’ exist in the form of numerous international courts and tribunals, such as the ICJ, the International Tribunal for the Law of the Sea, and ad hoc criminal tribunals. A key weakness, however, is that the jurisdiction of these bodies is typically based on the consent of the states involved. A state cannot usually be brought before the ICJ, for example, unless it has consented to the Court's jurisdiction. Hart himself described international law as a ‘primitive’ legal system because its secondary rules were not as developed as in a domestic system (Hart, 2012). Nevertheless, the existence of these rules, even in a decentralised form, provides a strong counterargument to the Austinian critique.
The Reality of Compliance
Perhaps the most compelling argument that international law is indeed law comes not from theory but from observing the behaviour of states. Sceptics often point to high-profile violations, such as an unprovoked invasion or a withdrawal from a major environmental treaty, as proof that international law is ineffective and therefore not ‘real’ law. However, as the legal scholar Louis Henkin famously observed, "almost all nations observe almost all principles of international law and almost all of their obligations almost all of the time" (Henkin, 1979, p. 47).
The focus on violations is misleading. News reports concentrate on breaches, not on the millions of routine instances of compliance that occur every day. International mail is delivered, aircraft fly across borders according to agreed-upon rules, and diplomats carry out their functions without interference. This day-to-day compliance is not primarily driven by the fear of sanctions, which, as noted, are often weak or non-existent. Instead, states comply for a variety of other reasons. One key reason is reciprocity; states obey the law because they want and expect other states to do likewise. For example, a state will protect foreign diplomats on its soil because it wants its own diplomats to be protected abroad.
Furthermore, a state's reputation is a valuable asset in international relations. Being perceived as a reliable, law-abiding member of the international community facilitates cooperation, trade, and diplomacy. Breaching international law can lead to a loss of credibility and influence. Finally, international law is often internalised into domestic legal systems and administrative practices. Government legal advisors routinely consult international law when formulating policy, ensuring that state actions are, for the most part, consistent with international obligations. This process of internalisation, what some scholars call the ‘management’ model of compliance, shows that states take their legal obligations seriously, treating them as law, not just as policy options (Chayes and Chayes, 1993).
Conclusion
The question of whether international law is ‘truly law’ ultimately depends on the definition of ‘law’ one chooses to adopt. If one insists on a narrow, Austinian definition based on a sovereign, commands, and sanctions, then international law will inevitably fall short. This model, however, is an inadequate description of law even within a domestic state, and it is an entirely inappropriate benchmark for a system designed to regulate interactions between sovereign equals.
A more realistic approach, as advocated by Hart and supported by the practice of states, is to view law as a system of rules that is accepted by its subjects as creating binding obligations. On this view, international law qualifies as a legal system. It has recognised sources for law-making, established institutions for adjudicating disputes (albeit with limitations), and it commands a high degree of compliance from states. States themselves treat it as law, creating it, invoking it in their disputes, and using it as a justification for their actions on the world stage. While it is undoubtedly a different kind of legal system from that found within a state, with significant weaknesses in its enforcement mechanisms, its fundamental character as a system of law is clear. It is a horizontal legal order, built on consent and reciprocity, rather than a vertical one built on command and coercion.
References
- Austin, J. (1832) The Province of Jurisprudence Determined.
- Chayes, A. and Chayes, A. H. (1993) 'On Compliance', International Organization, 47(2), pp. 175-205.
- Hart, H.L.A. (2012) The Concept of Law. 3rd edn. Oxford: Oxford University Press.
- Henkin, L. (1979) How Nations Behave: Law and Foreign Policy. 2nd edn. New York: Columbia University Press.
- Statute of the International Court of Justice (1945).
- Vienna Convention on the Law of Treaties (1969).
