Teachings as a Subsidiary Means for Determination the Rules of International Law according to Recent ILC Reports-Samira Maroof

Samira Maroof - L.L.M Student in International Law, Allameh Tabatabae’i University
2026/02/24

The framework for identifying and applying rules of international law is fundamentally formed by Article 38(1) of the Statute of the International Court of Justice, which figured the sources to be applied by the Court. Subparagraph (d) of this provision, explicitly recognizes "judicial decisions and the teachings of the most highly qualified publicists of the various nations as subsidiary means for the determination of rules of international law". This clause positions doctrine, commonly understood as "teachings" or scholarly writings, as a crucial auxiliary tool. Unlike primary sources such as treaties and customary international law, teachings do not possess law-creating authority. Instead, they serve to clear up, interpret, and confirm existing rules, particularly in situation where primary sources are ambiguous, silent, or evolving. In the context of international law's spread out and state-centric nature, teachings provide a scholarly lens that bridges gaps between practice and theory, ensuring a more coherent and progressive application of legal norms.

The International Law Commission (ILC), as the body responsible for the codification and progressive development of international law, has recently undertaken a dedicated study on this topic. In 2022, the topic “subsidiary means for the determination of rules of international law” was added to the ILC’s programme of work, and Charles Chernor Jalloh was appointed Special Rapporteur. His three successive reports represent a comprehensive and evolving analysis. Specifically, the First Report introduces the scope of the topic and surveys the ILC’s prior reliance on teachings. The Second Report delves into the auxiliary functions of subsidiary means, including the integration of teachings with judicial precedent. The Third Report, the most focused of the three, devotes an entire chapter to teachings (Chapter III, pp. 18–30), addressing their meaning, classification, and assessment of weight, and even proposing a draft conclusion on private expert groups (A/CN.4/781, Draft Conclusion 9, p. 28). Throughout the report, Jalloh underscores the role of teachings within a fragmented international legal landscape (Third Report, Chapter II.B, pp. 9–16), drawing on debates in the Sixth Committee of the General Assembly and the plenary discussions of the International Law Commission.

This article examines the role of teachings as a subsidiary means for the determination of rules of international law, drawing on these reports. It argues that teachings are not peripheral but central to the dynamism of international law, providing interpretive depth, fostering inclusivity, and helping to mitigate fragmentation. Building on the reports’ analyses, the discussion demonstrates how teachings have evolved from historical aids into contemporary normative guides that influence judicial decision-making, codification processes, and State practice within an increasingly complex global legal order.

Historical Context and the ILC's Previous Reliance on Teachings in the First Report

The First Report lays the groundwork for the topic by offering an in-depth exploration of the origins, nature, and scope of subsidiary means, with particular attention to teachings as a longstanding element of the ILC’s methodology. Chapter V, entitled “Previous work of the Commission on subsidiary means,” is especially significant, notably Subsection D: “The Commission’s reliance on teachings and the works of expert bodies.” In this section, Jalloh systematically documents how the International Law Commission has invoked teachings since its establishment in 1949, treating them as indispensable tools for clarifying ambiguities and supporting the progressive development of international law.

Jalloh begins by contextualizing teachings within Article 38(1)(d), tracing their roots to the French term "la doctrine" which covers scholarly writings by "the most highly qualified publicists" (A/CN.4/760, Chapter III.1, page 17); Chapter VII.A, page 72). He references the drafting history of the Statute of the Permanent Court of International Justice (PCIJ) by the 1920 Advisory Committee of Jurists, where teachings were escaped as tools "to establish the existence of a rule of law" when primary sources were insufficient (Ibid, para 214, page 72, quoting the Committee's minutes). This historical perspective positions teachings as "law-determining agencies" rather than formal sources (Ibid, Chapter VI.F, page 66), distinct from treaties or custom but essential for their identification.

The report catalogues extensive ILC practice, noting numerous references to doctrinal works in its yearbooks and commentaries (ibid., para. 122, p. 41). For example, during the codification of the Vienna Convention on the Law of Treaties, the International Law Commission drew on scholars such as Arnold McNair and Gerald Fitzmaurice to interpret principles including pacta sunt servanda (ibid., p. 42). Similarly, in its work on the law of State responsibility, reliance on Robert Jennings and Arthur Watts’ edition of Oppenheim's International Law helped delineate customary rules (ibid., para. 43, p. 43). Jalloh observes that “the Commission has consistently turned to teachings to clarify ambiguous provisions or to support progressive developments, demonstrating their practical utility as subsidiary means” (ibid., para. 51, p. 51, Chapter V.F).

Terminological precision is another key contribution. Jalloh clarifies that "teachings" should be confined to authoritative scholarly opinions, excluding partisan advocacy or non-academic writings, to maintain their objectivity. He addresses the absence of a formal hierarchy among sources (First Report ,Chapter VI.E, pages 64–66) , arguing that teachings can indirectly influence the formation of custom by evidencing opinio juris. He also advocates for greater inclusivity, emphasizing the need to incorporate teachings from non-Western scholars in order to address the Eurocentrism embedded in classical doctrine. This position reflects broader debates in the Sixth Committee of the General Assembly, where States such as Singapore and India have called for more diverse and representative perspectives. Although no specific draft conclusions on teachings were proposed at this introductory stage, Jalloh underscores their auxiliary function: “Teachings serve to confirm or elucidate rules rather than create them, yet their weight increases with the emergence of scholarly consensus.”

In sum, Chapter V.D (pp. 41–49) of the First Report establishes teachings as a cornerstone of the work of the International Law Commission, demonstrating their evolution from ad hoc references to more systematic tools in codification efforts. This foundation underscores their role in bridging theoretical analysis and practical State practice, thereby setting the stage for the functional and classificatory developments elaborated in the subsequent reports.

Developments on Functions and Precedent in the Second Report, with Implications for Teachings

Building on the First Report, the Second Report shifts to the operational dimensions of subsidiary means, emphasizing their auxiliary functions while situating teachings within a broader analytical framework. Chapter III, “Functions of subsidiary means for the determination of rules of international law,” reaffirms the non-creative character of teachings, while Chapter IV, “General nature of precedent in domestic and international adjudication,” draws instructive parallels between teachings and persuasive precedents, thereby enhancing their analytical utility.

In Chapter III.A, Jalloh revisits earlier discussions on functions, explicitly linking the analysis back to Chapter VI of the First Report. He records views expressed within the International Law Commission and in the Sixth Committee, noting that “teachings provide scholarly analysis that assists in identifying and interpreting rules, particularly in areas of emerging custom.” (Second Report, para 74-76, page 22, Chapter III.B). This auxiliary nature is confirmed by drafting history, where subsidiary means were designed to avoid rigidity in a custom-dominant system (Ibid, para. 86, page 26).

The report's focus on precedent indirectly amplifies teachings' importance. Jalloh contrasts common law's binding stare decisis with civil law's persuasive approach (Ibid, Chapter IV.A, pages 40–43), arguing that international tribunals treat both judicial decisions and teachings as subsidiary under Article 38(1)(d). Proposed Draft Conclusion 1 encapsulates this: "Subsidiary means serve to determine, but not to create rules of international law", explicitly including teachings.

Overall, the Second Report portrays teachings as dynamic complements to precedent, contributing to greater coherence in both adjudication and codification. In doing so, it builds upon the historical survey presented in the First Report and further refines the functional understanding of teachings as subsidiary means within the framework of the International Law Commission.

In-Depth Analysis of Teachings in the Third Report: Classification, Weight, and Proposed Guidelines

Jalloh’s Third Report offers a detailed look at how teachings fit into the framework of subsidiary means, focusing on their classification, the weight they carry, and practical guidelines for their use. The report defines teachings as scholarly works, such as books, articles, and commentaries produced by "the most highly qualified publicists," which analyze state practices and the sense of legal obligation (opinio juris). These works serve to support, not create, rules of international law, a role underscored by historical cases like the PCIJ’s Lotus decision (1927), where scholarly consensus helped clarify jurisdictional boundaries.

The report classifies teachings into three distinct categories: individual writings by single authors; private expert bodies and groups, such as the Institut de Droit International (Institute of International Law) (A/CN.4/781, para. 104, p. 24); and public or State-created/State-empowered expert bodies. This tripartite structure systematizes the diverse forms that teachings may assume and provides a coherent framework for their identification and application as subsidiary means. The weight accorded to such teachings depends on several factors, including the author’s expertise and authority, the degree of consensus among scholars, the relevance of the work to the legal issue at hand, and its independence from State influence.

A key proposal in the report extends the scope to include works from private expert groups, like the Harvard Draft Conventions, under Draft Conclusion 9. It suggests these can be considered teachings if they meet standards of authority and relevance. The report sets out clear criteria: the author’s qualifications, the rigor of their methods, how current the work is, and its freedom from government bias. This approach ensures teachings remain a reliable tool without overshadowing primary sources like treaties or customs.

The report further connects this analytical framework to broader systemic objectives, including the reduction of legal fragmentation. By aligning judicial reasoning with well-established doctrinal insights, teachings can help minimize the risk of inconsistent or conflicting rulings, a dynamic observable, for instance, in the jurisprudence of the ICJ. In this way, the framework not only guides the work of the ILC but also equips courts and expert bodies with principled criteria for the effective use of teachings. At the same time, it seeks to mitigate potential risks, such as bias in advisory contexts, by emphasizing scholarly rigor, methodological transparency, and independence from undue State influence.

Overall Role, Implications, and Coherence in International Law

Synthesizing the three reports, teachings emerge as flexible and persuasive aids within the meaning of Article 38(1)(d) of the Statute of the Court, complementing judicial decisions in the determination of rules of international law. The First Report establishes their historical reliance in the practice of the Commission; the Second integrates them more explicitly into the functional analysis of subsidiary means and the discussion of precedent; and the Third provides a clearer classification of teachings together with structured guidance on their weight and use. Taken together, the reports underscore the evolution of teachings from interpretive supplements to more structured instruments that promote inclusivity, coherence, and normative innovation within an increasingly complex international legal order.

The implications of the reports are multifaceted. Teachings serve as an important counterweight to fragmentation by synthesizing diverse sources and articulating coherent doctrinal frameworks. Draft Conclusion 12, which promotes “coherence in decisions of courts and tribunals” (A/CN.4/781, p. 71), implicitly reinforces the harmonizing function of doctrine within the broader system of sources. In a decentralized legal order lacking a supreme legislator, teachings contribute to a more pluralistic process of law determination, amplifying non-Western perspectives and helping to fill normative gaps in emerging fields such as space law and AI governance.

At the same time, challenges remain. The assessment of who qualifies as “highly qualified publicists” under Article 38(1)(d) of the Statute inevitably involves a degree of subjectivity, potentially perpetuating structural biases. Although the criteria outlined in Subsection E seek to mitigate this risk, careful application is required. Moreover, excessive reliance on teachings may blur the conceptual boundary between subsidiary means and primary sources of international law.

Ultimately, however, the three reports of the ILC affirm the indispensable role of teachings in fostering a coherent and more equitable international legal order—one capable of adapting to contemporary global challenges while remaining anchored in methodological rigor.

Conclusion

The three reports by Special Rapporteur Charles Chernor Jalloh collectively clarify the central role of doctrine or teachings as a subsidiary means for the determination of rules of international law. From the First Report’s historical survey of the ILC’s reliance on teachings, demonstrating their practical utility in codification, to the Second Report’s functional analysis emphasizing their auxiliary nature alongside precedent, and culminating in the Third Report’s detailed framework, including classification, criteria for assessing weight, and Draft Conclusion 9, the trajectory is clear: teachings are essential tools for interpreting and confirming rules within a fragmented legal order.

This evolution mirrors broader dynamics in international law. Teachings not only elucidate State practice and opinio juris, but also promote systemic unity, particularly by helping to reduce the risk of conflicting judicial decisions. Through proposed guidelines such as those set out in Subsection E, Jalloh strengthens the methodological clarity surrounding their use, ensuring their relevance for diverse stakeholders—judges, arbitrators, States, and scholars—while advocating greater inclusivity to move beyond Eurocentric limitations.

In an era of rapid globalization, in which challenges such as climate change, cyber threats, and the protection of human rights demand innovative legal responses, teachings provide a scholarly bulwark against uncertainty and normative gaps. The Commission’s work, informed by debates in the Sixth Committee, is poised to guide future practice and may influence the jurisprudence of the International Court of Justice as well as treaty negotiations. As Jalloh consistently emphasizes, a holistic and critical assessment of teachings enhances the process of law determination without displacing primary sources.

In conclusion, the three reports underscore that doctrine is not a relic of classical international law but a living instrument of its progressive development. By clarifying its subsidiary yet indispensable function, the International Law Commission contributes to a more coherent and equitable global legal system—one capable of remaining responsive to humanity’s shared challenges while grounded in methodological rigor. Policymakers and practitioners would do well to heed these insights and harness the full potential of teachings in shaping an international law that is both authoritative and adaptable.