International Law: Core Concepts

Introduction

International law is the body of rules and principles that governs relations among states and other actors recognized as having rights and obligations under international law. It provides frameworks for international cooperation, treaties, diplomacy, human rights, armed conflict, trade, territorial disputes and the peaceful settlement of disputes.

International law differs from domestic law because the international system does not have a single sovereign legislature, executive authority or universally compulsory enforcement system equivalent to those found within states. Its effectiveness depends on a combination of consent, reciprocity, institutions, domestic implementation, international pressure and other mechanisms.

What Is International Law?

International Law: A system of legal rules and principles governing relations among states and other recognized international actors.

Public International Law: The branch of international law governing relations involving states, international organizations and, in certain contexts, individuals and other actors.

Private International Law: Rules determining which country’s laws and courts apply to private disputes involving more than one jurisdiction.

International Legal Order: The collection of institutions, rules, principles and practices through which international legal relations are organized.

Principal Sources of International Law

Article 38 of the Statute of the International Court of Justice identifies major sources used by the Court in determining international law.

Treaty: A formal international agreement governed by international law.

International Custom: A general practice accepted as law.

Customary International Law: Rules arising from sufficiently general and consistent state practice accompanied by a belief that the practice is legally required.

Opinio Juris: The belief by states that a particular practice is followed because it is legally required.

General Principles of Law: General legal principles recognized across legal systems and used in international adjudication.

Judicial Decisions: Decisions of courts and tribunals that may serve as subsidiary means for determining rules of law.

Teachings of Publicists: Scholarly writings that may assist in identifying and interpreting international legal rules.

State Consent

Consent: Acceptance by a state of international legal obligations.

State Practice: The conduct of states relevant to the formation and interpretation of international law.

Persistent Objector: A state that consistently objects to an emerging customary rule and may, subject to the applicable legal conditions, avoid being bound by that rule.

Fundamental Principles

Sovereign Equality: The principle that states possess equal legal status regardless of differences in territory, population, wealth or military capability.

Non-Intervention: The principle restricting unlawful interference in matters falling within another state’s domestic jurisdiction.

Prohibition of the Use of Force: The general prohibition on the threat or use of force against states, subject to recognized exceptions and the applicable rules of international law.

Peaceful Settlement of Disputes: The principle that international disputes should be resolved through peaceful means.

Self-Determination: The right of peoples to determine their political status and pursue their economic, social and cultural development.

Good Faith: The principle that international legal obligations should be performed honestly and consistently with their legal purpose.

Pacta Sunt Servanda: The principle that treaties in force are binding upon the parties and must be performed in good faith.

Jurisdiction

Jurisdiction: The legal authority of a state or international institution to regulate conduct, adjudicate disputes or enforce law.

Territorial Jurisdiction: Jurisdiction based on conduct or persons located within a state’s territory.

Nationality Jurisdiction: Jurisdiction based on the nationality of the person involved.

Protective Jurisdiction: Jurisdiction asserted to protect important state interests from certain conduct occurring outside its territory.

Universal Jurisdiction: Jurisdiction exercised over certain particularly serious offences regardless of where they occurred or the nationality of the individuals involved, subject to applicable international and domestic law.

International Legal Personality

International Legal Personality: Capacity to possess rights and obligations under international law and to participate in international legal relations.

State as an International Person: States are the principal subjects of international law and possess extensive international legal rights and obligations.

International Organization: An organization established through an international agreement and possessing legal personality to the extent provided by its constituent instrument and applicable law.

Individual as a Subject of International Law: Individuals can possess rights and obligations directly under international law in areas such as human rights and international criminal law.

Responsibility

State Responsibility: The legal consequences arising when a state commits an internationally wrongful act.

Internationally Wrongful Act: Conduct attributable to a state that constitutes a breach of an international obligation.

Attribution: The process of determining whether conduct can legally be considered conduct of a state.

Breach: Failure to comply with an applicable international legal obligation.

Reparation: Measures intended to remedy injury caused by an internationally wrongful act.

Remedies

Restitution: Restoration of the situation that existed before the wrongful act, where possible.

Compensation: Monetary payment for legally established injury.

Satisfaction: Measures intended to address non-material injury, potentially including acknowledgment of wrongdoing or an expression of regret.

International Law and Domestic Law

Monism: A legal approach treating international and domestic law as parts of a single legal system.

Dualism: A legal approach treating international and domestic law as separate legal orders requiring domestic implementation in certain circumstances.

Domestic Implementation: Incorporation of international obligations into domestic law through constitutional, legislative or administrative mechanisms.

Compliance and Enforcement

International law may be implemented through:

• Diplomatic pressure
• Reciprocity
• International adjudication
• Arbitration
• Sanctions
• Countermeasures
• Domestic courts
• International organizations
• Monitoring mechanisms
• Political and reputational pressure

Compliance: Conduct by a state or other actor consistent with its international legal obligations.

Countermeasure: A measure that would otherwise be unlawful but may be justified under the rules of state responsibility when taken under specified conditions in response to another state’s internationally wrongful act.

Key Distinctions

International Law vs Domestic Law: International law governs international legal relations; domestic law primarily governs relations within a state.

Treaty Law vs Customary Law: Treaty law arises from agreements; customary law develops through general practice accepted as law.

Public vs Private International Law: Public international law primarily concerns states and international legal relations; private international law concerns cross-border private disputes.

Jurisdiction vs Sovereignty: Sovereignty refers to the supreme legal authority of a state within its recognized sphere; jurisdiction is the legal authority to regulate, adjudicate or enforce.

Key Terms at a Glance

International Law | Public International Law | Private International Law | Treaty | Customary International Law | State Practice | Opinio Juris | General Principles of Law | Sovereign Equality | Non-Intervention | Use of Force | Self-Determination | Pacta Sunt Servanda | Jurisdiction | Universal Jurisdiction | International Legal Personality | State Responsibility | Attribution | Breach | Reparation | Restitution | Compensation | Satisfaction | Countermeasure | Compliance

Related Glossaries

Treaties and International Agreements | Jurisdiction and State Responsibility | International Humanitarian Law | International Courts and Tribunals | Sovereignty | Self-Determination