Core Concepts of International Law and Constitutionalism

Posted on May 5, 2026 in Law

Nature of International Law

International law governs relations between states and between states and international organizations. Originally purely state-to-state, it now permeates domestic legal systems; human rights are applied in national courts, and investment tribunals affect corporations directly.

Key Structural Features

  • No global legislature: Law is created through the International Law Commission (ILC) and UN General Assembly (UNGA) resolutions.
  • No unified court: The ICJ, ICC, WTO tribunals, and regional courts coexist without a formal hierarchy.
  • No global police: Enforcement relies on UN peacekeeping, hybrid missions, and regional coalitions like NATO.

Core Principles

Three basic principles define the system: sovereign equality of states, non-interference in internal affairs, and the prohibition on the use of force, except for self-defence (Art. 51) or Security Council authorization (Art. 2(4)). Note that sovereign equality is often challenged by the P5 veto power and selective enforcement.

Perspectives on International Law

There are four primary views on the purpose of international law:

  • Instrument of power: Serves the interests of the strong.
  • Tool of emancipation: Gives a voice to the weak.
  • Self-preservation: Maintains system coherence.
  • Promise of justice: Keeps the hope of justice alive.

Henkin’s observation: “Almost all nations observe almost all principles of international law almost all of the time.”

Sources of International Law

A formal source creates binding law (e.g., a treaty), while a material source provides evidence that a rule exists without creating it (e.g., custom).

Article 38 ICJ Statute

  1. Treaties: Written agreements between states; only parties are bound.
  2. Custom: General practice accepted as law.
  3. General Principles: Principles recognized across national legal systems (e.g., good faith, equity) used to fill gaps.
  4. Subsidiary means: Judicial decisions and academic writings; these cannot create law and offer no binding precedent (Art. 59).

Customary Law

Custom requires two elements: state practice (what states actually do) and opinio juris (the belief that the practice is legally required). Persistent objectors are not bound if they object consistently from the start, whereas silence is interpreted as acquiescence.

Sovereignty and the State

The Peace of Westphalia (1648) ended the Thirty Years’ War and established the modern state system. A state is defined by three elements: sovereignty, government, and a territory with a permanent population.

Classical Sovereignty Theorists

  • Bodin: Absolute, perpetual power.
  • Hobbes: Absolute sovereignty via social contract.
  • Locke: Limited sovereignty derived from consent.
  • Rousseau: Popular sovereignty guided by the general will.

Constitutionalism

A constitution regulates the allocation of powers and defines the relationship between the government and the public. It divides power between the executive, legislative, and judiciary branches.

Key Characteristics

  • Prior to government: Must exist before the government is formed.
  • Constituent power: Authority derives from the people.
  • Superiority: Prevails over ordinary law.
  • Entrenchment: Requires special processes for amendment.

Formal vs. Material Constitutionalism

Formal constitutionalism views the constitution as the highest norm in the legal hierarchy. Material constitutionalism argues that a constitution must also be democratic and liberal to be legitimate; otherwise, it is considered a “facade” constitution.

Fundamental Rights

Fundamental rights originate from two traditions: Natural Law (pre-existing human dignity) and Positive Law (rights created by legal systems). Rights are categorized into three generations:

  • 1st Generation: Civil and political rights (negative rights/prohibitions).
  • 2nd Generation: Economic, social, and cultural rights (positive rights requiring state action).
  • 3rd Generation: Collective rights (e.g., self-determination, healthy environment).

Modern democracies balance these rights, recognizing that they serve as both a limit on state power and a precondition for legitimate governance.