International Law II
2024 — 2025
Pagina 1 van 83
,Content:
• Introduction and Methodology of International Law
• Sources of International Law
• International obligations
• The Responsibility of States for Internationally Wrongful Acts
• Enforcement of International Law
I. Methodology of International Law
Doing international legal research: a method is a distinct way to determine what the law is for practical
purposes
Looking for answers to international legal questions within the international legal system
Legal research in international law is both similar to and different from legal research in domestic law:
(a) Similar: basic requirements
You need a research question
You need to understand the problem you are approaching (both in terms of the legal doctrine
and its underlying theory)
You need a method to answer your question
You need to rely on primary and secondary sources
(b) Different: research in international law is different because international law is practiced
everywhere
There is no “single” international law: for this reason it is an area of law that is almost always
contested
International law is not hierarchical: several legal frameworks might apply to one single
question (fragmentation)
International law’s sources include customary law; which is difficult to pinpoint
In conclusion: this makes describing “the law” as an object of research much trickier
§1. Research questions
Three families of research questions:
Pagina 2 van 83
,Finding a research question will be one of the most important and challenging parts of your research: every
research has a question at its foundation
The research question is simply the question that your research seeks to answer
Three families of questions:
(a) Descriptive questions: seek to tell us something about the legal world as it is
It seeks to describe “the law” as it is, whether in abstract or in relation to a specific situation
(b) Normative questions: ask what ought to be the state of things in relation to law
Aks what the law ought to be, whether in general or in a specific instance
Difficulty with normative questions: to answer them, we need external parameters for
assessing law, in other words we need a theory on what is considered “good”, in light of
which we can present an argument about what the law should be
We cannot draft from facts alone what ought to be: it is here where theory plays a key role
→ normative legal theories are there to help us articulate our benchmarks for assessiong
what law should be
(c) Critical questions: seek to expose the relations between law and power and are somewhat in the
middle between descriptive and normative questions
Inquire into the power relations that shape law or into the relations between law and politics
in the broad sense of the term: in this sense, they aim to be descriptive: they seek to
describe law as a product of power relations and the manner in which law conceals and
neutralizes political choices
Like normative scholarship, critical research questions also rely on theories (critical legal
theories)
Crucial to understand: both normative and critical research questions usually have descriptive subquestions
§2. Primary and secondary sources
Primary sources (hard law): treaties, customary international law (state practice and opinio iuris), general
principles of international law, unilateral acts of states and international organisations (…)
Primary sources comprise raw information or first-hand accounts of something: they give you direct,
unmediated access to the objective of your research
Secondary sources: case law, teachings of the most highly qualified publicists (doctrine), soft law
Secondary sources are writings about primary sources: they interpret primary sources for you
Help you find primary rules of international law: they can never be higher than the primary sources
and can only be used to find them and to interpret them
II. Sources of International Law
I. Introductory remarks
Where does international law come from, and how is it made?
Pagina 3 van 83
, These are difficult questions to answer: transferring ideas from national legal systems to a very
different context of international law is dangerous
There is no Code of International Law: International Law has no Parliament en nothing that can be
described as legislation
In international law, there exist similar secondary rules as in national legal systems, but they
are less clearly defined, for a number of reasons: there is, for example, at the international
level neither a universal legislative body corresponding to a national Parliament, nor a
system of universal judicial jurisdiction which has built up a wide-ranging body of precedent
Difficult to determine when exactly a secondary rule acquired the status of a rule of exiting,
binding law: prior to that moment, it forms part of what is called lex feranda (law which ought
to be made, i.e. developing or embryonic law), thereafter it is part of the lex lata (law which
has been made, positive law)
Rules can only be made on the basis of the consent of the States: confirmed in the Lotus Case
(France v. Turkey, 1927)
“International law governs relations between independent States. The rules of law binding
upon States, therefore, emanate from their own free will as expressed in conventions or
by usages generally accepted as expressing principles of law and established in order
to regulate the relations between these co-existing independent communities or with a view
to the achievement of common aims. Restrictions upon the independence of States cannot,
therefore, be presumed.”
Horizontal structure of international society and the problem of sources:
The principle of sovereignty of States makes it impossible to impose international rules on States
The role of the ‘state’s will’ in the formation of international norms becomes therefore fundamental
There is no formal hierarchy between the sources of international law
II. Sources of international law
Two types of sources:
(a) Formal source
Process through which legal rules come into being
Methods for creating rules of general application which are legally binding on their
adressees (Article 38 ICJ Statute)
The question of the authority for the rule as a rule of law, binding on States, is determined by
the formal source of the rule: the generally recognized formal sources are idenitified in
Article 38 ICJ Statute
Two most important sources: (a) treaties and (b) international custom (see later in detail)
If a rule is laid down in a treaty, then it is binding on the States parties to that treaty,
and the treaty is at once the material and formal source of that rule
That rule may, however, be taken over and applied in the practice of other States,
not parties to that treaty, in such a way, and to such an extent, that it takes on the
character of a customary rule: for these States, the material source of the rule will be
the wording of the original treaty, but the formal source will be international custom
(b) Material source
Pagina 4 van 83
2024 — 2025
Pagina 1 van 83
,Content:
• Introduction and Methodology of International Law
• Sources of International Law
• International obligations
• The Responsibility of States for Internationally Wrongful Acts
• Enforcement of International Law
I. Methodology of International Law
Doing international legal research: a method is a distinct way to determine what the law is for practical
purposes
Looking for answers to international legal questions within the international legal system
Legal research in international law is both similar to and different from legal research in domestic law:
(a) Similar: basic requirements
You need a research question
You need to understand the problem you are approaching (both in terms of the legal doctrine
and its underlying theory)
You need a method to answer your question
You need to rely on primary and secondary sources
(b) Different: research in international law is different because international law is practiced
everywhere
There is no “single” international law: for this reason it is an area of law that is almost always
contested
International law is not hierarchical: several legal frameworks might apply to one single
question (fragmentation)
International law’s sources include customary law; which is difficult to pinpoint
In conclusion: this makes describing “the law” as an object of research much trickier
§1. Research questions
Three families of research questions:
Pagina 2 van 83
,Finding a research question will be one of the most important and challenging parts of your research: every
research has a question at its foundation
The research question is simply the question that your research seeks to answer
Three families of questions:
(a) Descriptive questions: seek to tell us something about the legal world as it is
It seeks to describe “the law” as it is, whether in abstract or in relation to a specific situation
(b) Normative questions: ask what ought to be the state of things in relation to law
Aks what the law ought to be, whether in general or in a specific instance
Difficulty with normative questions: to answer them, we need external parameters for
assessing law, in other words we need a theory on what is considered “good”, in light of
which we can present an argument about what the law should be
We cannot draft from facts alone what ought to be: it is here where theory plays a key role
→ normative legal theories are there to help us articulate our benchmarks for assessiong
what law should be
(c) Critical questions: seek to expose the relations between law and power and are somewhat in the
middle between descriptive and normative questions
Inquire into the power relations that shape law or into the relations between law and politics
in the broad sense of the term: in this sense, they aim to be descriptive: they seek to
describe law as a product of power relations and the manner in which law conceals and
neutralizes political choices
Like normative scholarship, critical research questions also rely on theories (critical legal
theories)
Crucial to understand: both normative and critical research questions usually have descriptive subquestions
§2. Primary and secondary sources
Primary sources (hard law): treaties, customary international law (state practice and opinio iuris), general
principles of international law, unilateral acts of states and international organisations (…)
Primary sources comprise raw information or first-hand accounts of something: they give you direct,
unmediated access to the objective of your research
Secondary sources: case law, teachings of the most highly qualified publicists (doctrine), soft law
Secondary sources are writings about primary sources: they interpret primary sources for you
Help you find primary rules of international law: they can never be higher than the primary sources
and can only be used to find them and to interpret them
II. Sources of International Law
I. Introductory remarks
Where does international law come from, and how is it made?
Pagina 3 van 83
, These are difficult questions to answer: transferring ideas from national legal systems to a very
different context of international law is dangerous
There is no Code of International Law: International Law has no Parliament en nothing that can be
described as legislation
In international law, there exist similar secondary rules as in national legal systems, but they
are less clearly defined, for a number of reasons: there is, for example, at the international
level neither a universal legislative body corresponding to a national Parliament, nor a
system of universal judicial jurisdiction which has built up a wide-ranging body of precedent
Difficult to determine when exactly a secondary rule acquired the status of a rule of exiting,
binding law: prior to that moment, it forms part of what is called lex feranda (law which ought
to be made, i.e. developing or embryonic law), thereafter it is part of the lex lata (law which
has been made, positive law)
Rules can only be made on the basis of the consent of the States: confirmed in the Lotus Case
(France v. Turkey, 1927)
“International law governs relations between independent States. The rules of law binding
upon States, therefore, emanate from their own free will as expressed in conventions or
by usages generally accepted as expressing principles of law and established in order
to regulate the relations between these co-existing independent communities or with a view
to the achievement of common aims. Restrictions upon the independence of States cannot,
therefore, be presumed.”
Horizontal structure of international society and the problem of sources:
The principle of sovereignty of States makes it impossible to impose international rules on States
The role of the ‘state’s will’ in the formation of international norms becomes therefore fundamental
There is no formal hierarchy between the sources of international law
II. Sources of international law
Two types of sources:
(a) Formal source
Process through which legal rules come into being
Methods for creating rules of general application which are legally binding on their
adressees (Article 38 ICJ Statute)
The question of the authority for the rule as a rule of law, binding on States, is determined by
the formal source of the rule: the generally recognized formal sources are idenitified in
Article 38 ICJ Statute
Two most important sources: (a) treaties and (b) international custom (see later in detail)
If a rule is laid down in a treaty, then it is binding on the States parties to that treaty,
and the treaty is at once the material and formal source of that rule
That rule may, however, be taken over and applied in the practice of other States,
not parties to that treaty, in such a way, and to such an extent, that it takes on the
character of a customary rule: for these States, the material source of the rule will be
the wording of the original treaty, but the formal source will be international custom
(b) Material source
Pagina 4 van 83
