Week 2

Public International Law - Sources

• Permissive System: International law operates on a permissive principle, meaning actions are not prohibited unless explicitly forbidden. This is embodied in the Lotus case and the principle nullum crimen sine lege (no crime without law).

Sources of International Law

• Domestic Law Sources: Include constitution, legislation, civil codes, executive branch enforcement mechanisms (police, judiciary), and sovereignty.

• International Law Sources: Include treaties, customary international law, general principles of law, judicial decisions, scholarly writing, soft law, and jus cogens.

Sources - Article 38 ICJ Statute (International Court of Justice)

• Treaties: Establish rules explicitly recognized by contesting states.
• Custom: Evidence of general practice accepted as law (consistent and uniform state practice with opinio juris—a sense of legal obligation).
• General Principles: Fundamental legal principles recognized by most legal systems.
• Judicial Decisions and Scholarship: Subordinate sources used to determine rules.

Customary International Law

• Nature: Unwritten rules or customs that states adhere to.
• Formation: Habit of consistent pattern of state practice → tradition, expectation → legal obligation.
• Example: The North Sea Continental Shelf cases highlight State practice and opinio juris in determining customary international law.

Customary International Law (Art. 38(1)(b) ICJ Statute)

• State Practice: Behavior of states must be general, widespread, settled, and consistent.
• Opinio juris: State activity driven by a belief that the practice is legally required, often demonstrated via statements, correspondence, or UNGA votes.

Binding Customary International Law

• Persistent Objector Rule: A state that persistently objects to the development of a customary international law is not bound by it, but this requires clear, sustained objection.

Sources of International Law: Summary

• Primary Formal Sources: Treaties, custom, general principles, (jus cogens).
• Primary Material Sources: State practice, opinio juris, judicial decisions (less authoritative).
• Secondary Material Sources: Scholarly writing.
• Formal Sources: Recognized methods of creating international law.
• Material Sources: Underpinning factors influencing international law.

General Principles of Law

• Nature: Fundamental legal principles recognized across legal systems.
• Role: Used when specific treaty or customary law isn't applicable. They often relate to issues like due diligence, accountability and are a supplementary role—derived from judicial decisions or scholarship.
• Example: The Corfu Channel case illustrates the application of a general principle of due diligence (obligation to exercise reasonable care and address harms to other states).

Summary of Custom

• States adhere to consistent practice: Often due to a sense of legal obligation.
• Widespread and repeated practice: By significant numbers of states over lengthy time frames.
• Disadvantages: Can be challenging to prove. Often not specific.