Important Theories of under International Law
Key Takeaways
- Theories of international law explain why international law exists, why States regard it as binding and where its legal authority comes from.
- The two broad traditional approaches are Natural Law Theory and Positivist Theory. Natural law links international law with reason, justice and universal principles, while positivism focuses on identifiable legal rules arising from recognised legal processes and social facts.
- Consent Theory explains international obligations primarily through the consent of States, particularly through treaties and, in classical accounts, customary international law.
- Self-Limitation Theory, associated with Georg Jellinek, argues that sovereign States can voluntarily restrict the exercise of their sovereignty and thereby accept international obligations.
- Common Will Theory, associated particularly with Heinrich Triepel, argues that international law arises from the common or united will of States rather than the isolated will of a single State.
- The principle of pacta sunt servanda establishes that treaties in force are binding and must be performed in good faith. This principle is expressly recognised in Article 26 of the Vienna Convention on the Law of Treaties, 1969.
- Modern international legal theory goes beyond the question of why law is binding and includes approaches such as realism, Marxism, feminism, the New Haven School, Third World Approaches to International Law, constructivism and law and economics.
What Are Theories of International Law?
Theories of international law are different explanations of the nature, authority, origin and functioning of international legal rules. They attempt to answer a basic jurisprudential question: Why are States legally bound by international law when there is no world legislature or central sovereign equivalent to a national government?
This question becomes important because international law operates differently from municipal law. Within a State, legislation can be enacted by a recognised legislature and enforced through domestic institutions. International law largely operates in a decentralised international system consisting of sovereign States, international organisations, courts and other actors.
Add LawBhoomi as your preferred source on Google.
Article 38(1) of the Statute of the International Court of Justice identifies international conventions, international custom and general principles of law among the materials the Court applies when deciding disputes according to international law. Judicial decisions and teachings of highly qualified publicists are described as subsidiary means for determining rules of law. These are generally discussed as the sources of international law.
Theories of international law, however, deal with a different question. Rather than merely identifying the sources of international law, they attempt to explain why those sources create binding legal obligations.
Why Are Theories of International Law Important?
Theoretical approaches make it easier to understand several fundamental issues in Public International Law.
They help explain:
Find the latest legal internship opportunities, updated daily.
- why sovereign States accept restrictions imposed by international rules;
- whether consent is necessary before international law becomes binding;
- whether morality and justice form part of the foundation of international law;
- how treaties and customary international law acquire legal force;
- the relationship between sovereignty and international obligation;
- whether international and municipal law form separate or connected legal systems; and
- how political, economic, colonial, social and institutional forces influence international law.
No single theory completely explains every feature of modern international law. Different theories instead highlight different aspects of the international legal system.
Natural Law Theory
What Is Natural Law Theory in International Law?
Natural Law Theory holds that certain legal principles arise from reason, justice, morality or universal principles that exist independently of the will of individual States.
Under this approach, the authority of international law cannot be explained entirely through agreements between States. Some principles are regarded as capable of having a foundation beyond mere governmental consent.
Natural law has one of the oldest intellectual traditions in international legal thought. Naturalist approaches generally maintain that principles of right and wrong can transcend particular political systems and can be understood through reason.
Thinkers associated with the development of natural-law ideas in international law include Francisco de Vitoria, Hugo Grotius and other early jurists, although their individual theories differed considerably. Historical scholarship recognises the significant role played by natural-law reasoning in the development of international law.
Main Features of Natural Law Theory
Natural Law Theory generally emphasises that:
- law cannot always be separated completely from justice and morality;
- certain principles may exist independently of specific State consent;
- reason can provide a basis for legal obligation; and
- international society requires principles applicable beyond individual political communities.
The theory historically contributed to ideas concerning universal legal obligations, but modern international law does not simply identify international legal rules by asking whether they are morally desirable.
Criticism of Natural Law Theory
One major criticism is the difficulty of objectively identifying what constitutes natural justice or universal reason. Different societies and thinkers may disagree about moral principles.
Explore the latest legal opportunities for law students and lawyers.
Modern international law therefore relies heavily on identifiable legal sources and accepted methods of determining legal rules rather than morality alone.
Positivist Theory of International Law
What Is Positivist Theory?
Positivism explains law by reference to recognised legal sources, social facts and valid law-making processes rather than morality alone.
International legal positivism became particularly influential during the nineteenth and twentieth centuries. Lassa Oppenheim is closely associated with the development of a State-centred positivist approach to international law. His approach placed substantial emphasis on treaties, custom and the common consent of States while distinguishing the existence of law from questions concerning whether a rule was morally desirable.
Positivism therefore asks whether a rule has become legally valid through recognised legal processes rather than whether the rule is inherently just.
Major Features of Positivism
Traditional positivist approaches generally emphasised:
- sovereignty of States;
- identifiable sources of international law;
- State practice and international agreements;
- separation between law and morality; and
- objective determination of existing legal rules.
However, modern international legal positivism is broader than the simple proposition that every rule must arise directly from express State consent. Contemporary scholarship identifies several varieties of positivist thought, including social, system-based and functional approaches.
Consent Theory
Why Is International Law Binding According to Consent Theory?
Consent Theory, sometimes described in connection with voluntarism, argues that States are bound by international legal obligations because they have consented to them.
The clearest example is a treaty. When States validly become parties to a treaty, they accept legal obligations created by that treaty. The formation, interpretation, amendment and termination of such agreements form part of the broader law of treaties in international law.
Consent may therefore operate through mechanisms such as:
Learn at your own pace with LawBhoomi's recorded law courses.
- express acceptance of treaty obligations;
- participation in recognised international law-making processes; and
- State practice accompanied by acceptance of the practice as law in the formation of customary international law.
Classical positivist thought often placed particularly strong emphasis on consent and State will. The Permanent Court of International Justice’s decision in the S.S. Lotus case (France v. Turkey) became closely associated with this voluntarist understanding of international law, although modern international law cannot be reduced entirely to the strongest version of the Lotus approach.
Limitations of Consent Theory
Consent Theory faces difficulties when attempting to explain every international obligation.
For example, modern international law recognises the importance of customary rules and certain peremptory norms, while international institutions also operate through legal structures that cannot always be explained simply as a fresh act of individual consent by every affected State.
Consent remains extremely important, but it is not universally regarded as a complete explanation of the entire international legal order.
Self-Limitation Theory
What Is the Self-Limitation Theory?
The Self-Limitation or Auto-Limitation Theory is particularly associated with Georg Jellinek.
It attempts to resolve an apparent contradiction: if a State is sovereign, how can international law impose binding restrictions upon it?
The answer offered by this theory is that sovereignty includes the capacity of the State to limit its own freedom of action. A State can voluntarily accept restrictions and thereafter become bound by them.
Jellinek’s theory sought to reconcile the sovereign will of the State with the obligatory nature of international law.
Criticism of Self-Limitation Theory
The principal difficulty is that, if the legal obligation ultimately depends only upon the continuing will of the State, it becomes difficult to explain why the State cannot simply withdraw that limitation whenever it chooses.
International law generally treats valid legal obligations as binding according to their governing rules rather than as obligations that disappear merely because one party changes its mind.
Common Will Theory
What Is Common Will Theory?
The Common Will Theory is closely associated with Heinrich Triepel.
Triepel attempted to move beyond the idea that international law comes from the independent will of one State. According to this approach, international legal rules can arise from a common will of several States.
The combined will is therefore different from the individual will of each participating State. Triepel used the idea of a common or united will to explain how objective international rules could arise among sovereign States.
Importance of Common Will Theory
The theory improves upon strict individual voluntarism because international law is inherently concerned with relationships among multiple members of the international community.
However, questions remain regarding rules binding States that have not specifically participated in creating a particular common will.
Pacta Sunt Servanda Theory
What Does Pacta Sunt Servanda Mean?
Pacta sunt servanda means that agreements must be kept.
In treaty law, the principle has a precise contemporary legal foundation. Article 26 of the Vienna Convention on the Law of Treaties, 1969 provides that every treaty in force is binding upon its parties and must be performed by them in good faith.
Article 27 further provides, subject to Article 46, that a party cannot rely upon its internal law as justification for failure to perform a treaty.
The principle therefore performs a fundamental role in maintaining stability and reliability in treaty relations.
Anzilotti and Pacta Sunt Servanda
Dionisio Anzilotti is closely associated with positivist theories concerning international obligation and pacta sunt servanda. Historical jurisprudential discussions have treated the principle as one proposed explanation for the binding force of international legal commitments.
A theoretical difficulty nevertheless arises: if pacta sunt servanda explains why agreements are binding, another question follows—why is the rule of pacta sunt servanda itself binding?
For this reason, the principle is highly important to treaty law but does not necessarily provide a complete philosophical explanation of the entire international legal system.
Hans Kelsen’s Pure Theory of Law
What Is Kelsen’s Theory of International Law?
Hans Kelsen developed the Pure Theory of Law, one of the most influential positivist theories of the twentieth century.
Kelsen attempted to study law as a system of norms without deriving its legal validity from morality, politics or sociology. He distinguished what the law is from what law morally ought to be.
According to the Kelsenian approach, legal norms form a normative structure in which the validity of one norm is connected with another higher norm. At the foundation of the legal system lies a presupposed fundamental norm, commonly called the Grundnorm or basic norm.
Kelsen’s approach was important because it moved away from the proposition that sovereign State will must necessarily provide the ultimate basis of international law.
Kelsen and Monism
Kelsen is also closely associated with a monistic understanding of international and municipal law.
Monism treats national and international law as belonging to a single overall legal structure rather than as completely separate legal orders. The distinction between monism and dualism is central to understanding the relationship between international law and municipal law.
This approach contrasts with dualist theories that regard international law and municipal law as separate systems.
Sociological and Social Necessity Approaches
Can International Law Be Explained by International Society?
Another explanation focuses on the existence of an international community and the practical necessity of legal regulation.
States do not exist in complete isolation. Trade, security, diplomatic relations, environmental concerns, communications, migration, international organisations and numerous other matters create continuing relationships among members of the international community.
International law can therefore be viewed partly as a response to social interdependence.
Even some writers traditionally associated with positivism recognised that the existence of States within an international community created important social foundations for international law.
The social-necessity approach is valuable because it explains why international legal regulation develops even in the absence of a central world sovereign.
Theory of Fundamental Rights of States
An older theoretical approach attempted to explain international relations through certain fundamental or inherent rights of States.
Traditional international legal thought sometimes referred to ideas such as:
- independence;
- equality;
- self-preservation; and
- respect for territorial and political existence.
The theory sought to derive rules governing relations among States from characteristics considered inherent in statehood.
Its importance today is mainly historical. Contemporary international legal rights and obligations are determined through recognised international legal rules rather than merely by assuming an abstract set of natural rights belonging to States.
Natural Law and Positivism: What Is the Difference?
The distinction between the two approaches can be stated simply.
Natural Law Theory asks whether international legal principles have a foundation in reason, justice or universal norms. Positivism primarily asks whether a rule is legally valid according to recognised processes and sources of international law.
Natural law therefore provides a value-oriented explanation, while positivism traditionally provides a source-oriented or system-oriented explanation.
The distinction should not be overstated. The history of international legal thought contains substantial interaction between natural-law and positivist traditions, and individual scholars cannot always be placed neatly into one category. Modern scholarship recognises that international legal positivism itself contains several different approaches.
Modern Theoretical Approaches to International Law
Traditional theories mainly concentrated on the binding force and validity of international law. Modern international legal theory asks broader questions concerning power, institutions, economics, gender, colonial history, political behaviour and decision-making.
Contemporary international legal theory includes a wide range of approaches such as natural law, positivism, realism, constructivism, Marxist theory, policy-oriented approaches, law and economics, feminist approaches and cosmopolitan theories.
Realist Approaches
Realist approaches examine the relationship between international law and political power. They question whether legal rules can be understood without considering the strategic interests and power relationships of States.
Marxist Approaches
Marxist theories examine international law in connection with economic structures, capitalism, class relations, ideology and imperialism.
Modern Marxist international legal scholarship has particularly examined the relationship between international law and international capitalism, theories of imperialism and the position of the Third World within international legal structures.
Feminist Approaches
Feminist approaches analyse how international legal institutions and doctrines interact with gender and structural inequality.
Feminist international legal scholarship has examined areas such as human rights, armed conflict, peace and security, international institutions and the ways in which apparently neutral rules may affect different groups differently.
Third World Approaches to International Law
Third World Approaches to International Law (TWAIL) examine international law through the historical experiences of colonialism, imperialism and global inequality.
TWAIL scholarship studies both the historical development of the international legal order and its continuing effects upon States and peoples of the Global South.
New Haven School
The New Haven School adopts a policy-oriented understanding of international law. Instead of examining legal rules only as formal commands, it considers international law as part of a broader process of decision-making involving authority, policy and social values.
Constructivist Approaches
Constructivist approaches examine how norms, identities, ideas and social interactions influence the behaviour of international actors.
They provide an important connection between international legal theory and international relations scholarship.
Traditional and Modern Theories Serve Different Purposes
Traditional and modern theories should not be treated as answering exactly the same question.
Traditional theories such as consent, self-limitation, common will and pacta sunt servanda principally attempt to explain:
Why is international law legally binding?
Broader contemporary approaches such as Marxism, feminism, realism, constructivism and TWAIL ask questions such as:
How does international law operate? Who shapes it? What historical, political, economic and social forces influence it? Who benefits from particular international legal arrangements?
This distinction makes the study of international legal theory considerably clearer.
Conclusion
Theories of international law provide different explanations for the authority, validity and operation of the international legal system. Natural Law Theory derives international obligation from broader principles of reason and justice, while Positivist Theory places greater emphasis on recognised legal sources and law-making processes.
Within positivist and voluntarist traditions, Consent Theory, Self-Limitation Theory, Common Will Theory and pacta sunt servanda attempt in different ways to reconcile State sovereignty with binding international obligations. Hans Kelsen’s Pure Theory of Law provides a different normative explanation by treating law as a structured system of valid norms rather than making sovereign State will the necessary ultimate foundation of international law.
Modern international legal theory has expanded considerably beyond the traditional debate. Realist, Marxist, feminist, constructivist, policy-oriented and Third World approaches analyse international law in light of power, institutions, history, economics, identity and inequality.
No single theory fully explains contemporary international law. Together, however, these theories provide a framework for understanding why international legal rules are regarded as binding, how those rules develop and how international law functions within an increasingly complex international community.
Join LawBhoomi’s 100K+ Community
