Lexicon: Sources of International Law

Introduction

Focus on sources of international law
Brief historical context
- 1920: Establishment of League of Nations with the Permanent Court of International Justice
- 1945: United Nations and the International Court of Justice (ICJ) established
- ICJ replaced the previous court (PCIJ)

International Conventions (Treaties)
- Defined as international agreements between states, in written form, governed by international law
- Can cover any subject matter
- States agree to rules when signing
- Notable treaties:
  - 20th Century: Molotov-Ribbentrop Pact, United Nations Charter, North Atlantic Treaty (NATO), Schengen Agreement
  - 21st Century: Minsk Protocol (2014), Paris Agreement (First Climate Agreement), Brexit Withdrawal Agreement
International Custom
- Evidence of a general practice accepted as law
- Two elements:
  1. General practice: becomes common among states
  2. Accepted as law (opinio juris): belief of a legal obligation
- Governs areas not covered by treaties
General Principles of Law
- Abstract in nature, no precise list
- Examples:
  - Good faith: conduct should be honest and fair
  - Respect for human dignity: important in humanitarian and human rights law
  - Principle of proportionality: actions should be proportionate to aims
- Two approaches:
  1. Autonomous and separate from treaties and customs
  2. Part of treaty law and customary international law
Judicial Decisions and Teachings
- Article 38: Subsidiary means for determination of rules of law
- Supplementary means for interpretation, application, and development of law

Primary vs Secondary Sources:
- Some view treaties and customs as primary
- International Law Commission includes general principles as primary
No hierarchical relationship among main sources
- Treaty law, customary international law, and general principles are equal