The Systemic Function of General Principles (International Law)

by Stephan Kinsella on February 9, 2026

Interesting recent lecture by Prof Mads Andenæs and Prof Johann Ruben Leiss, University of Oslo, ‘The Systemic Function of General Principles’ – Prof Mads Andenas & Prof Johann Ruben Leiss, University of Oslo (Feb. 6, 2026). See their paper Article 38(1)(d) ICJ Statute and the Principle of Systemic Institutional Integration; also General Principles and the Coherence of International Law – Principes Généraux Et Cohérence Du Droit International; The Law and Politics of the General Principles of Law in the Twenty-First Century.

Lecture summary: The lecture explores the systemic function of general principles in international law in light of the ongoing work of the ILC on general principles of law and recent practice of international courts and tribunals, such as the Climate Change Advisory Opinion of the International Court of Justice from 2025. In its first part, the lecture examines the ILC’s approach to the systemic function of general principles and comments of states on the ILC’s work. In its second and third part, the lecture discusses the two main features of the systemic function of general principles, namely their contribution to inter-norm and inter-systemic coherence in international law. All general principles potentially fulfil a systemic function by their gap-filling role and inter-systemic communication through Article 38(1)(c) ICJ Statute. Several general principles have a systemic pull in inter-norm contexts as interpretative guidelines and inter-norm harmonisers and coordinators. In the relationship between different (sub)orders of international law (including European law and national legal orders applying international law), several principles provide for ‘hinge’ mechanisms and inter-system harmonisers which open legal (sub)orders to one another, and integrate them into (relative) unity, while others serve as inter-system coordinators or mechanisms for conditional closure of legal orders. This means, all general principles have a systemic function, whereas certain principles have more direct systemic function by virtue of their normative content. Through their systemic function, general principles contribute as a central cohesive force furthering international law’s character as a legal and (relative) unitary system. This system is characterized by a complex and dynamic interplay between a plurality of legal norms, orders, and sub-orders, including national legal orders, through systemic principles of openness, coordination, and conditional closure.

Grok summary report:

Final Comprehensive Report: General Principles of Law in International Law

(Consolidated Synthesis – February 2026)

Executive Summary

This consolidated report integrates all prior analyses, including the International Law Commission’s (ILC) ongoing codification work on general principles of law (2018–2025), key academic papers by Mads Andenas and co-authors, the Andenas/Leiss lecture on systemic functions, relevant ICJ jurisprudence, and the ILC draft conclusions (first reading 2023, second reading provisional adoption May 2025). It provides:

an overview of the ILC project and its 2025 draft conclusions
summaries of the attached scholarly papers and lecture
a detailed explanation of the relationship and functions of general principles (autonomy, coherence roles, and Conclusion 12)
a concise, non-exhaustive list of recognized or frequently invoked general principles
discussion of the outdated “civilized nations” phrase in Article 38(1)(c) of the ICJ Statute
brief consideration of potential relevance to libertarian legal theory, particularly the “Universal Principles of Liberty” (emphasizing good faith, arbitration, and conflict avoidance) and related contract-law arguments (good faith, unconscionability, implicit duties)

The central theme is that general principles serve as a foundational, gap-filling, and coherence-promoting source of international law—autonomous yet interactive with treaties and custom—helping to maintain a relatively unitary system amid normative and institutional fragmentation.

1. The ILC Project on General Principles of Law

Mandate and Progress

The ILC, a UN expert body established in 1947, studies “General principles of law” under Article 38(1)(c) of the ICJ Statute (“the general principles of law recognized by civilized nations”). The topic was added to the active agenda in 2018; Special Rapporteur Marcelo Vázquez-Bermúdez submitted four reports (2019–2025).

2023 (74th session): First reading adoption of 11 draft conclusions + commentaries (A/78/10, Chapter IV; advance PDF: https://legal.un.org/ilc/reports/2023/english/a_78_10_advance.pdf; Chapter IV: https://legal.un.org/ilc/reports/2023/english/chp4.pdf)
2025 (76th session): Provisional second-reading adoption of 12 conclusions by the Drafting Committee (A/CN.4/L.1018, May 2025: https://legal.un.org/docs/?symbol=A/CN.4/L.1018); full adoption with commentaries deferred to 2026 due to shortened session
Analytical Guide & Landing Pages: https://legal.un.org/ilc/guide/1_15.shtml (topic hub); https://legal.un.org/ilc/reports/2023 (2023 report overview); https://legal.un.org/ilc/reports/ (main archive)

Core Features of the 2025 Draft Conclusions (A/CN.4/L.1018)

Scope: Concern general principles as a source of international law
Recognition: Principles are rules recognized as such
Categories: (a) derived from national legal systems; (b) formed within the international legal system
4–6. Identification & Transposition (national-derived): comparative analysis + compatibility/suitability
Identification (international-formed): recognized by the community of nations as intrinsic
8–9. Subsidiary means: judicial decisions & teachings aid identification
Relationship to other sources: distinct from treaties/custom; interpret, supplement, confirm
Functions: contribute to coherence; basis for substantive/secondary/procedural rules; interpret/complement; resorted to when other rules fail
(New) Place in general international law: form part of general international law

No exhaustive list of principles is provided—examples remain illustrative and drawn from practice.

2. Relationship and Functions of General Principles (Detailed Elaboration)

Relationship to Other Sources

Draft Conclusion 10 affirms autonomy: general principles are a separate, non-hierarchical source. They are not merely gap-fillers subordinate to treaties or custom; they can coexist, interpret, supplement, or confirm rules from those sources.

Example: pacta sunt servanda underlies VCLT Article 26 but retains independent force.
Systemic integration (VCLT Art. 31(3)(c)) exemplifies how principles harmonize without supremacy conflicts.
Compatibility with jus cogens is required; lex specialis may displace in narrow contexts.

Functions Contributing to Coherence

Draft Conclusion 11 states principles “may contribute to the coherence of the international legal system,” a function arising naturally from gap-filling (avoiding non liquet).

They operate through four main roles:

Substantive rights and obligations — establish core duties (e.g., no-harm, elementary considerations of humanity)
Secondary rules — govern creation/modification/enforcement (e.g., pacta sunt servanda, rebus sic stantibus)
Procedural rules — ensure fair process (e.g., res judicata, iura novit curia)
Interpretive rules — clarify norms (e.g., good faith in VCLT interpretation, systemic integration)

All principles potentially aid coherence; certain ones (good faith, pacta sunt servanda, due diligence) exert stronger systemic “pull” due to normative content.

New Conclusion 12 (“General principles of law form part of general international law”) affirms their foundational status, responding to fragmentation concerns and reinforcing their role in a relatively unitary system.

3. Summaries of Key Scholarly Contributions

Andenas & Leiss (2016 draft): Article 38(1)(d) embodies systemic institutional integration via cross-referencing among courts, complementing substantive coherence.
Andenas & Chiussi (2017 concept note): Principles counter fragmentation from treaties/custom; act as gap-fillers, convergences, potential jus cogens/erga omnes norms.
Andenas & Stone Sweet (draft): Judge-made principles enhance effectiveness and coherence across regimes; ICJ/ILC evolution reflects progressive adaptation amid politicization risks.
Lecture (Andenas & Leiss): Systemic function via intra/inter-systemic coherence; principles as hinges (openness), coordinators (lex specialis), and conditional closures; all contribute, some strongly (good faith, pacta sunt servanda).

4. Concise List of Candidate General Principles

(Non-exhaustive; drawn from ILC reports, ICJ/PCIJ/arbitral practice, and scholarly sources)

Abuse of rights
Burden of proof
Due diligence
Elementary considerations of humanity
Equity
Estoppel
Freedom of maritime communication
Good faith
Iura novit curia
Lex posterior
Lex specialis
Lis pendens
No-harm principle
Non-use of territory for harmful acts
Nullum crimen / nulla poena sine lege
Pacta sunt servanda
Pendente lite
Prohibition of unjust enrichment
Rebus sic stantibus
Res judicata
Respect for human dignity
Right to lawyer-client confidentiality
Separation of companies and shareholders
Systemic integration
Uti possidetis

Recognition occurs case-by-case via comparative analysis (national-derived) or community acceptance (international-formed).

5. The Phrase “Recognized by Civilized Nations”

The wording in Article 38(1)(c) dates from the 1920 PCIJ Statute and reflects early-20th-century Eurocentric hierarchy. Modern practice (ICJ, ILC) interprets it inclusively as “common to the various legal systems of the world,” emphasizing geographical and legal-family diversity. The ILC drafts avoid the phrase entirely, focusing on representativeness and compatibility. The expression remains formally in the Statute but is effectively neutralized to align with decolonized, universal international law.

6. Potential Relevance to Libertarian Legal Theory

The ILC framework—autonomous principles promoting coherence through good faith, gap-filling, and interpretive harmony—offers conceptual parallels to voluntary, polycentric legal orders.

Universal Principles of Liberty (esp. Art. IV §1): The pledge to negotiate in good faith, prefer arbitration over force, avoid self-help/vigilante justice, and bind security providers to shared norms mirrors international law’s use of good faith and procedural principles (res judicata, systemic integration) to maintain order without central coercion. ILC autonomy/non-hierarchy resonates with principles as a consensual “supreme baseline” for decentralized enforcement.
Good Faith & Unconscionability in Contract: The implicit duty of good faith to prevent unfair “fine print” exploitation parallels the ILC’s interpretive/supplementary role of good faith (e.g., reasonable performance). Gap-filling and coherence functions could analogize to libertarian adjudication implying terms parties “would have reasonably agreed to,” rejecting unconscionable clauses as inconsistent with voluntary consent.

In both contexts, general principles function as organic, reason-based norms that reduce conflict and sustain trust in non-state or minimally coercive systems—aligning with libertarian emphasis on voluntary interaction and emergent order.

Conclusion

General principles of law remain a dynamic, judge-developed source that fills gaps, interprets norms, and promotes systemic coherence without rigid hierarchies. The ILC’s methodological focus (identification, categories, functions) and illustrative examples provide a robust framework for understanding their evolving role in international law—and, by analogy, in any legal order that values reason, consent, and conflict minimization over centralized command.

Primary Sources

ILC Analytical Guide: https://legal.un.org/ilc/guide/1_15.shtml
2025 Draft Conclusions: A/CN.4/L.1018
2023 First Reading: A/78/10, Chapter IV
Andenas et al. papers and lecture materials as previously summarized

“To cite but a few examples, in the Corfu Channel case, the International Court of Justice found that the use of indirect evidence, in addition to being admitted in “all systems of law”, was “recognized by international decisions”. 44 In Pedra Branca/Pulau Batu Puteh, the Court similarly noted that “[i]t is a general principle of law, confirmed by the jurisprudence of this Court, that a party which advances a point of fact in support of its claims must establish that fact”. 45 In the Chagos Marine Protected Area arbitration, the tribunal noted that the “frequent invocation [of the principle of estoppel] in international proceedings has added definition to the scope of the principle”. 4… The European Court of Human Rights and the Inter-American Court of Human Rights have likewise relied on prior decisions to justify the existence of the principle iura novit curia. 47 In international criminal law, prior decisions by international courts and tribunals have also played a significant role in the identification of general principles of law.48″ … “27 A general principle of law that is often referred to in practice and in the literature, and which may be considered to be of a general and abstract character, is the principle of good faith. …
28 Examples of general principles of law that have been invoked or applied in practice, and which may be considered to be of a more specific character (because they present, for instance, precise conditions for their application), include the principles of res judicata and lis pendens, and the right to lawyer-client confidentiality. See, respectively, International Court of Justice, Question of the Delimitation of the Continental Shelf between Nicaragua and Colombia beyond 200 Nautical Miles from the Nicaraguan Coast (Nicaragua v. Colombia), Preliminary Objections, Judgment, I.C.J. Reports 2016, p. 100, at pp. 125–126, paras. 58–61; Permanent Court of International Justice, Certain German Interests in Polish Upper Silesia, Judgment, 25 August 1925, P.C.I.J. Series A, No. 6, pp. 5 et seq., at p. 20; International Court of Justice, Questions relating to the Seizure and Detention of Certain Documents and Data (Timor‐Leste v. Australia), Provisional” .. “Examples of such general principles of law may include pacta sunt servanda, good faith, the principles of lex specialis and lex posterior, respect for human dignity and elementary considerations of humanity.” [↩]