International Judicial Monitor
Published by the International Judicial Academy, Washington, D.C., with assistance from the
American Society of International Law

Winter 2014 Issue

General Principles of International Law


General Principles of International Law:  Monism and Dualism

Carolyn A. Dubay

By: Carolyn A. Dubay, Associate Editor, International Judicial Monitor and Assistant Professor of Law, Charlotte Law School

The conventional wisdom in international law is that a state can accept and integrate international law into the domestic system in one of two ways.  In a monist legal system, international law is considered joined with and part of the internal legal order of a state.  In a dualist legal system, on the other hand, international law stands apart from national law, and to have any effect on rights and obligations at the national level, international law must be domesticated through legislative process.   The tension between these competing views of international law reached its height in Europe between World War I and World War II, when legal scholars began to seriously question how and to what extent binding international legal obligations and formal international institutions could minimize the threat of war.  At its core, however, the distinction between a monist and dualist theory rests between two competing and important goals.  Specifically, monist theory prioritizes the desirability of a formal international legal order to establish the rule of law among nations, while dualist theory prioritizes the notions of individual self-determination and sovereignty at the state level.

Under a monist model, international law serves not merely as a legal framework to guide state-to-state relations in the international sphere, but as a source of law integrated into and superior to domestic law.  As such, a properly ratified or accepted treaty forms part of the national legal regime.  An important consequence of this understanding of the role of international law is that it may be applied and enforced directly in domestic courts without the necessity of domestic implementation.  This framework thus creates a single and unitary legal system, with international law at the top of the legal order and local, municipal law subordinate.   The monist view is attributed most often to the work of Austrian legal scholar Hans Kelsen, who advocated in the 1920s for the primacy of international law as a derivative of natural law, rather than as merely an expression of the individual decisions of states to be bound by certain norms through customary practice.  Ultimately, Kelsen’s monist theory was intended to promote international peace by creating binding obligations enforceable against state actors in formal international justice institutions, as indicated in his famous work, Peace Through Law (1944).

At the same time that Kelsen was attempting to redefine the relationship between the state and the international legal order, dualist legal theories emerged as the theoretical counterpart to Kelsen’s unitary vision of law.   Under a dualist model, there is a dichotomy between international legal obligations that states as sovereigns agree to recognize in their foreign relations, and domestic legal rules that are binding in internal relationships between the state and its citizens or subjects.  Accordingly, international law can only have binding legal force at the domestic level if it is implemented at the national or local level.  One of the most notable proponents of the dualist theory of international law was German scholar Heinrich Triepel, who argued that international law was a manifestation of the "common will" of sovereign states.   As such, there was a complete separation between international law and state law.   From this theory, the common understanding of dualism has emerged that international law is not supreme to domestic law, and the relevance of international law in the domestic legal regime is a question left to the local political processes.  For example, under this framework, a treaty takes effect and is binding in international relations once it is executed by the head of state.  To be binding at the domestic level, and enforceable in a domestic court, the treaty must be specifically implemented through appropriate legislation.


Despite continued academic interest in the impact of the monism v. dualism debate, in reality most nations have a blend of monist and dualist approaches to international law.  The status of international law in the United States reflects this mix of approaches.  In terms of constitutional sources of authority, Article VI of the United States Constitution clearly states that the “Constitution, and the laws of the United States which shall be made in pursuance thereof; and all treaties made, or which shall be made, under the authority of the United States, shall be the supreme law of the land; and the judges in every state shall be bound thereby, anything in the Constitution or laws of any State to the contrary notwithstanding.”  This express incorporation of treaties into binding (and supreme) domestic law was complemented by the understanding that customary international law “is part of our law,” as famously noted in the United States Supreme Court’s decision in The Paquete Habana, 175 U.S. 677 (1900).  With the advent of formal international institutions in the 20th century and the explosion in the number, variety and scope of international agreements, however, the United States has adopted an increasingly dualist approach to the place of international law in the domestic sphere.  Most recently, questions have emerged as to the democratic legitimacy of international law and decisions of international tribunals.  On a more practical level, in the wake of the United States Supreme Court’s decision in Medellin v. Texas, 552 U.S. 491 (2008) involving the domestic enforceability of the Vienna Convention of Consular Affairs, and in the Guantanamo Bay detainee cases involving the domestic application of the Geneva Conventions, translation of treaty obligations into judicially enforceable rules often turns on whether a treaty obligation is regarded as self-executing or non-self-executing. 

Despite the mixing of monist and dualist perspectives in both national and international politics, the competing ideologies of Kelsen and Triepel bear out the best way of advancing the rule of law in the international sphere.  The competition of ideas has led to continued scholarly and juridical interest in the question as to how and under what circumstances international legal norms that advance the goals of human rights, economic development and world peace can be enforced in a democratic and politically legitimate manner.


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with assistance from the American Society of International Law.

Editor: James G. Apple.
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