Introduction
Public international law (PIL) and international relations (IR) are two interconnected fields that play a pivotal role in shaping global governance and state interactions. While PIL provides a legal framework to regulate the conduct of states and international actors, IR explores the political, economic, and social dynamics that underpin these interactions. This essay examines the intricate relationship between PIL and IR, arguing that they are mutually reinforcing disciplines that both reflect and influence global order. By exploring their conceptual overlap, practical interdependence, and areas of tension, the essay will demonstrate how these fields complement each other in addressing complex international issues. Additionally, it will consider their limitations in achieving consistent outcomes in a fragmented global system. The discussion is rooted in academic literature and aims to provide a balanced analysis suitable for an undergraduate exploration of this interdisciplinary topic.
Conceptual Foundations: Defining Public International Law and International Relations
To understand the relationship between PIL and IR, it is essential to define their respective domains. Public international law, often simply termed international law, consists of rules and principles that govern the conduct of states, international organisations, and, to some extent, individuals in the international arena. It encompasses areas such as treaty law, human rights, and the law of armed conflict, deriving authority from sources like treaties, customary practices, and general principles of law (Cassese, 2005).
International relations, on the other hand, is a social science discipline that studies the interactions between states, non-state actors, and global institutions. It draws on theoretical frameworks such as realism, liberalism, and constructivism to explain phenomena like diplomacy, conflict, and cooperation (Baylis, Smith, and Owens, 2020). While PIL provides a normative structure for state behaviour, IR seeks to explain why states act as they do, often highlighting the role of power, interest, and ideology.
The relationship between the two fields is evident at a conceptual level. PIL is often shaped by the political realities studied in IR, while IR frequently engages with legal norms as tools or constraints in international affairs. For instance, the creation of international treaties often reflects political negotiations and power dynamics central to IR scholarship (Reus-Smit, 2004). This symbiosis suggests that neither field can be fully understood in isolation, as each informs the other’s scope and relevance.
Mutual Reinforcement: Law as a Tool of International Relations
One of the primary ways in which PIL and IR interact is through the use of law as a mechanism for achieving IR objectives. International law serves as a tool for states to formalise agreements, manage conflicts, and establish frameworks for cooperation. The United Nations Charter, for example, is a legal document that codifies principles of state sovereignty and collective security—key concerns of IR. It emerged from the political will to prevent another global conflict after World War II, illustrating how IR challenges can lead to legal innovation (Shaw, 2017).
Furthermore, PIL often provides legitimacy to IR initiatives. The establishment of international organisations like the World Trade Organization (WTO) relies on legal agreements that reflect broader IR goals of economic integration and globalisation. States use these legal structures to navigate power imbalances and pursue national interests, a dynamic central to realist IR perspectives (Baylis, Smith, and Owens, 2020). Indeed, the legalisation of international norms can stabilise relations between states, reducing uncertainty—an outcome highly valued in IR theory.
However, the effectiveness of PIL in supporting IR objectives is not without limitations. Legal rules may be ignored when they conflict with powerful states’ interests, as seen in instances where Security Council vetoes block enforcement of international norms. This highlights a key tension: while PIL can reinforce IR goals, its impact is often contingent on political will, a factor IR scholars frequently emphasise (Reus-Smit, 2004). Thus, while there is mutual reinforcement, the relationship is not always harmonious.
International Relations Shaping Public International Law
Just as PIL supports IR, the reverse is equally true: IR shapes the development and enforcement of international law. The political context studied in IR often determines the content and evolution of PIL. For instance, the post-Cold War era saw a surge in human rights law, driven by a liberal IR consensus on the importance of individual freedoms and democratic governance (Cassese, 2005). Treaties like the Rome Statute, which established the International Criminal Court in 1998, reflect a shift in global political priorities, influenced by IR dynamics such as the rise of transnational advocacy networks.
Moreover, IR theories provide critical insights into why certain legal norms emerge or fail. Realism, for example, suggests that powerful states dominate the creation of PIL, often crafting rules to serve their interests. The unequal application of international law, such as in the selective enforcement of war crimes prosecutions, supports this view (Shaw, 2017). Conversely, constructivist IR scholars argue that shared values and identities can lead to stronger legal norms, as seen in the widespread acceptance of anti-slavery laws over time (Reus-Smit, 2004). These perspectives illustrate how IR not only influences PIL but also helps explain its successes and shortcomings.
Despite this influence, IR does not always align seamlessly with PIL development. Political divisions, such as those between developed and developing states, can hinder consensus on legal norms, as evidenced by ongoing debates over climate change agreements like the Paris Accord. This demonstrates that while IR shapes PIL, it can also complicate its universality and enforcement, revealing a nuanced relationship.
Tensions and Limitations in the Relationship
While PIL and IR often complement each other, tensions arise due to their differing priorities and methodologies. PIL is inherently normative, aiming to establish binding rules for state behaviour, whereas IR is descriptive and analytical, often prioritising power over morality. This fundamental difference can lead to discrepancies. For instance, while PIL prohibits the use of force except in self-defence or with Security Council approval, realist IR scholars argue that states frequently act unilaterally based on national interest, as seen in the 2003 Iraq War (Baylis, Smith, and Owens, 2020). Such actions undermine legal authority, exposing PIL’s dependence on political realities.
Additionally, the fragmented nature of the international system poses challenges for both fields. PIL lacks a central enforcement mechanism, making compliance voluntary in many cases—a problem IR scholars attribute to the anarchic nature of global politics (Cassese, 2005). Similarly, cultural and ideological differences between states, a focus of IR analysis, can obstruct the universal application of PIL, as seen in varying interpretations of human rights obligations. These tensions suggest that while the two fields are interlinked, their relationship is not always productive or straightforward.
Arguably, another limitation lies in their respective scopes. PIL often struggles to address non-state actors like terrorist groups or multinational corporations, which are central to contemporary IR. Although developments like international criminal law attempt to bridge this gap, the legal framework remains state-centric, somewhat misaligned with the broader, more fluid concerns of IR (Shaw, 2017). This discrepancy highlights an area where the relationship between PIL and IR requires further alignment to address modern global challenges effectively.
Conclusion
In summary, the relationship between public international law and international relations is one of mutual influence and interdependence, marked by both synergy and tension. PIL provides a structured framework to support IR objectives such as cooperation and conflict resolution, while IR shapes the content and enforcement of international law through political, economic, and social dynamics. However, their differing approaches—normative versus analytical—can lead to friction, particularly when political interests override legal obligations or when legal frameworks fail to adapt to contemporary IR challenges. The implications of this relationship are significant for global governance, as neither field can fully address international issues without the other. For students of law and politics, understanding this interplay is crucial to grasping the complexities of the international system and advocating for reforms that strengthen both legal norms and political cooperation. Ultimately, while PIL and IR are distinct, their interconnectedness underscores the need for an interdisciplinary approach to studying and addressing global challenges.
References
- Baylis, J., Smith, S., and Owens, P. (2020) The Globalization of World Politics: An Introduction to International Relations. 8th ed. Oxford University Press.
- Cassese, A. (2005) International Law. 2nd ed. Oxford University Press.
- Reus-Smit, C. (2004) The Politics of International Law. Cambridge University Press.
- Shaw, M. N. (2017) International Law. 8th ed. Cambridge University Press.
