Sources of International Law — Article 38, ICJ Statute — KSLU Pil Notes

Sources of International Law — Article 38, ICJ Statute

flowchart TD
    ART38[Article 38 - ICJ Statute] --> PRIMARY[Primary Sources]
    ART38 --> SUBSIDIARY[Subsidiary Sources]
    PRIMARY --> T[Treaties and Conventions]
    PRIMARY --> C[International Custom]
    PRIMARY --> GP[General Principles of Law]
    SUBSIDIARY --> JD[Judicial Decisions - subsidiary]
    SUBSIDIARY --> JW[Writings of Jurists - subsidiary]
    T --> T1[UN Charter, UNCLOS, Geneva Conventions, VCLT]
    C --> C1[State Practice + Opinio Juris]
    GP --> GP1[Good faith, Res Judicata, Equity]
    JD --> JD1[ICJ, PCIJ - not binding as precedent but persuasive]
    JW --> JW1[Oppenheim, Starke, Grotius]

1. Treaties

The most important source in modern IL — like statutes in domestic law
Only binding on parties who have signed and ratified (pacta tertiis nec nocent nec prosunt)
Governed by Vienna Convention on Law of Treaties, 1969
Examples: UN Charter (1945), UNCLOS (1982), Geneva Conventions (1949)

2. Custom — Two Essential Elements

North Sea Continental Shelf Cases (ICJ, 1969): Custom requires (1) State practice — widespread, consistent, and general; and (2) Opinio Juris — belief that the practice is legally obligatory, not merely courteous.

Element	Meaning	Example
State Practice	Long, consistent, general behaviour by States	Diplomatic immunity observed for centuries
Opinio Juris	States act because they believe it is legally required	Not just habit — a legal obligation
Duration	No fixed period — can form quickly if practice is widespread	Nuclear weapons — practice still forming
Persistent Objector	State that consistently objects is not bound	Iceland’s fishing zone objection (1970s)

3. General Principles of Law

Principles common to most domestic legal systems — applied in IL when treaties and custom are silent:

Good faith (bona fides)
Res judicata — final judgment is binding
Ne bis in idem — no double jeopardy
Equity and unjust enrichment
Due process

4. Judicial Decisions (Subsidiary)

ICJ judgments are binding only on parties to that case (Art 59, ICJ Statute)
But carry great persuasive authority — cited in subsequent cases
Key cases: S.S. Lotus, Corfu Channel, North Sea Continental Shelf, Nicaragua

5. Writings of Jurists (Subsidiary)

Grotius (Father of IL), Vattel, Oppenheim, Starke, Brierly
Used to fill gaps — not binding but respected by courts