PUBLIC INTERNATIONAL LAW
Week 1: the nature and structure of international law
International law wasn’t built in one day, but it evolved gradually during history:
A long time ago, kings ruled territories, but their power was influenced by the Pope, knights, and
merchants, who operated across borders. People often felt more connected to these transnational
communities than to their own nations. During this time, two legal ideas shaped society: natural
law (a universal moral code) and jus gentium (the law of nations). Since rulers were individuals, they
too were subject to natural law.
As European explorers set sail to distant lands, conflicts arose. The Spanish conquistadors claimed
vast territories in the Americas, leading to violent clashes with native peoples. A Dominican
professor, Francesco da Vitoria, argued that these indigenous people were part of the international
community and that the Spanish must justify their wars based on law, not just on "discovery" or papal
grants.
By the 17th century, certain thinkers started shaping international law into a structured system. He
helped define how nations should interact and resolve disputes. But the real turning point came
in 1648, when the Peace of Westphalia ended the Thirty Years' War. This treaty changed everything.
For the first time, sovereign states became the main actors in the international system. No longer were
empires or the church the primary rulers of Europe; each state was independent, sovereign and equal
under the law. People began to feel stronger ties to their own countries, and international relations
became more organized.
As the world entered the 19th century, international law took a new direction. This was the era of
positivism, where law was not based on morality but on the will of the state. If a state did not consent
to a law, it was not bound by it. Treaties and customs became the main ways states created legal
obligations. This period also saw the first multilateral treaties on war and peace. Countries agreed on
rules for armed conflicts, leading to the establishment of the Permanent Court of Arbitration, where
disputes could be settled without war.
The early 20th century was marked by two devastating world wars. After World War I, the
international community created the League of Nations to maintain peace. However, it lacked
enforcement power and failed to prevent World War II.
After the war, world leaders learned from past mistakes and established the United Nations ans t
he UN Charter introduced key principles:
• The prohibition of war unless authorized by the Security Council.
• The Security Council’s authority to maintain peace.
• The General Assembly, where all states could express their concerns.
• The International Court of Justice (ICJ), replacing the previous Permanent Court.
At the same time, new international organizations emerged. For instance, the NATO ensured
collective defense, while the European Union (EU) worked to unify European nations economically
and politically.
Before 9/11 a lot of international law was on interstate relations or on human rights, but individuals
weren’t seen as a threat to world peace, only states. However, when 9/11 happened, this ceearted a
whole new area and challenges for states, because how were they supposed to deal with terrorism?
,In domestic law you have states, nationals and companies. The state regulates the relationship
between these two, that rights and obligations they have. You can regulate national law by having the
police, judges etc. International law regulates the relationship between states. It also impacts nationals
and companies, but it is essentially about the regulation of relations between states as equal actors
National law regulates disputes between citizens of a sovereign state or between the citizens and the
state. However, when the issue concerns the interest of more than one state, national law is not
suitable for settling the dispute and one must find the answer in international law. So where national
law falls short, international law enters the picture
There are two ways in which this can happen:
1. When two or more states have a colliding interest in the subject (inhoud) of the issue (for
example: determination of the border of a country, this interest the aligning countries as well)
2. When involved states have agreed in a treaty to turn the issue into one of an international
character (the states have a mutual goal, so they use the form of international law to do this
together and make a treaty
International legal obligations should be considered a logical consequence of sovereignty. There are
multiple sovereign States, which justifies the existence of international law. Just like the freedom of
individuals within a state must be limited in order to ensure freedom for all individuals, the same goes
for sovereign States. For a peaceful coexistence of sovereign States, rules are needed that govern how
States may behave in their mutual relations
States can usually decide for themselves how they’ll implement its international commitments
→ there are two ways in which international law is applied in the national legal systems by the
legislature and national courts:
¨ Monist approach = the state has domestic law, which states that international law will have a
direct effect in domestic law, once the state has ratified it at an earlier moment in time. The
international law is applicable in the national law. Is has direct working/effect. If there is a
conflict between national and international law, then international law prevails national law
→ a single a coherent legal system. International law is directly applicable in the national legal
system
¨ Dualist approach = the international law doesn’t have direct effect in national law once the
state has ratified it. The international law has to be integrated in/transported to national law in
order to be effective. If there is an international treaty it does not directly apply, it must be
transferred into a national law first and if there’s a conflict between national and international
law, national law prevails.
→ two separate legal systems that operate individually. National legislation is adopted to give
effect to international law, so international law must be converted or transformed via a separate
law
¨ Pluralist approach = relationship between the two systems. This is more complex and
diverse
effect to international law
→ if you get a question on this, use the words: direct effect and supremacy
In the Netherlands you can rely on provisions from international treaties before national courts,
because the Netherlands has opted for a monist system and therefore the international law
automatically becomes part of the national legal order
→ however, the Netherlands has a moderate monistic system, as only the treaties that are binding for
everyone have direct effect (article 94 Gw)
, Why do we have international law?
• Coexistence = states need to regulate certain issues in order to coexist together. This can’t be
done under national law fully because you can give effect to some rules, but you can’t
regulate how certain things happen. You need to sit with other states and agree to make
certain rules, especially because of the fact that there are a lot of common
threats/opportunities. So, it’s concerned with the basic rules that allow states to exist
peacefully alongside each other
→ international law of coexistence = provides the legal answers to questions that are inherently of
interest to more than one state and is required to separate the powers of the sovereign states and
thereby uphold peaceful coexistence. This law is focuses on the matter in which sovereign states
interact among each other and is therefore primarily horizontal. It merely seeks to ensure that states
can pursue their different and separate issues without disrespecting the sovereignty and rights of other
states. In this case two or more states can have colliding interests in the substantive structure of
international law.
• Cooperation = states can’t coexist without regulating that field of law, but they want to
cooperate. They want to make progress together and therefore they want to regulate certain
issues. So, this goes beyond coexistence to promote collaboration between states in various
areas. It covers areas where states work together to adress common challenges
→ international law on cooperation = provides the legal answers to questions that aren’t inherently
at interest to two or more state but have nevertheless become a matter of international concern
through the adoption of a treaty. It has got to do with the adoption of treaties between States, with
which the issues might be turned into an international matter due to its content
The difference between the international law of coexistence and the international law of cooperation
is that the latter is optional for sovereign States. This means that States can decide for themselves
whether they want to turn matters that were initially governed by national law into a matter of
international law
How does international law work?
You have sovereignty and consent. This means that on the first hand the states have supreme power
over their territory and may not be the subject to the jurisdiction of other state. Moreover, states must
consent to be bound by international rules, without consent they can’t be bound
→ states are considered to be sovereign, so there’s no authority above them. This means that laws can
only be made with their consent and because they’re sovereign they also have the possibility to do this
In international law you don’t have a constitution or a police, so the power is very much horizontally;
states agree to do something together. The absence of an international legal system of enforcement is
characteristic of the international legal order. The lack of a central system means that no central body
can be identified that makes laws/rules. In a national system, the government imposes sanctions when
a legal rule is violated, while in international law, states comply with the rules that result from mutual
agreements, because they consider this to be important and therefore the enforcement lies with the
states themselves. However, sometimes this is done by international organizations, like the UN
Week 1: the nature and structure of international law
International law wasn’t built in one day, but it evolved gradually during history:
A long time ago, kings ruled territories, but their power was influenced by the Pope, knights, and
merchants, who operated across borders. People often felt more connected to these transnational
communities than to their own nations. During this time, two legal ideas shaped society: natural
law (a universal moral code) and jus gentium (the law of nations). Since rulers were individuals, they
too were subject to natural law.
As European explorers set sail to distant lands, conflicts arose. The Spanish conquistadors claimed
vast territories in the Americas, leading to violent clashes with native peoples. A Dominican
professor, Francesco da Vitoria, argued that these indigenous people were part of the international
community and that the Spanish must justify their wars based on law, not just on "discovery" or papal
grants.
By the 17th century, certain thinkers started shaping international law into a structured system. He
helped define how nations should interact and resolve disputes. But the real turning point came
in 1648, when the Peace of Westphalia ended the Thirty Years' War. This treaty changed everything.
For the first time, sovereign states became the main actors in the international system. No longer were
empires or the church the primary rulers of Europe; each state was independent, sovereign and equal
under the law. People began to feel stronger ties to their own countries, and international relations
became more organized.
As the world entered the 19th century, international law took a new direction. This was the era of
positivism, where law was not based on morality but on the will of the state. If a state did not consent
to a law, it was not bound by it. Treaties and customs became the main ways states created legal
obligations. This period also saw the first multilateral treaties on war and peace. Countries agreed on
rules for armed conflicts, leading to the establishment of the Permanent Court of Arbitration, where
disputes could be settled without war.
The early 20th century was marked by two devastating world wars. After World War I, the
international community created the League of Nations to maintain peace. However, it lacked
enforcement power and failed to prevent World War II.
After the war, world leaders learned from past mistakes and established the United Nations ans t
he UN Charter introduced key principles:
• The prohibition of war unless authorized by the Security Council.
• The Security Council’s authority to maintain peace.
• The General Assembly, where all states could express their concerns.
• The International Court of Justice (ICJ), replacing the previous Permanent Court.
At the same time, new international organizations emerged. For instance, the NATO ensured
collective defense, while the European Union (EU) worked to unify European nations economically
and politically.
Before 9/11 a lot of international law was on interstate relations or on human rights, but individuals
weren’t seen as a threat to world peace, only states. However, when 9/11 happened, this ceearted a
whole new area and challenges for states, because how were they supposed to deal with terrorism?
,In domestic law you have states, nationals and companies. The state regulates the relationship
between these two, that rights and obligations they have. You can regulate national law by having the
police, judges etc. International law regulates the relationship between states. It also impacts nationals
and companies, but it is essentially about the regulation of relations between states as equal actors
National law regulates disputes between citizens of a sovereign state or between the citizens and the
state. However, when the issue concerns the interest of more than one state, national law is not
suitable for settling the dispute and one must find the answer in international law. So where national
law falls short, international law enters the picture
There are two ways in which this can happen:
1. When two or more states have a colliding interest in the subject (inhoud) of the issue (for
example: determination of the border of a country, this interest the aligning countries as well)
2. When involved states have agreed in a treaty to turn the issue into one of an international
character (the states have a mutual goal, so they use the form of international law to do this
together and make a treaty
International legal obligations should be considered a logical consequence of sovereignty. There are
multiple sovereign States, which justifies the existence of international law. Just like the freedom of
individuals within a state must be limited in order to ensure freedom for all individuals, the same goes
for sovereign States. For a peaceful coexistence of sovereign States, rules are needed that govern how
States may behave in their mutual relations
States can usually decide for themselves how they’ll implement its international commitments
→ there are two ways in which international law is applied in the national legal systems by the
legislature and national courts:
¨ Monist approach = the state has domestic law, which states that international law will have a
direct effect in domestic law, once the state has ratified it at an earlier moment in time. The
international law is applicable in the national law. Is has direct working/effect. If there is a
conflict between national and international law, then international law prevails national law
→ a single a coherent legal system. International law is directly applicable in the national legal
system
¨ Dualist approach = the international law doesn’t have direct effect in national law once the
state has ratified it. The international law has to be integrated in/transported to national law in
order to be effective. If there is an international treaty it does not directly apply, it must be
transferred into a national law first and if there’s a conflict between national and international
law, national law prevails.
→ two separate legal systems that operate individually. National legislation is adopted to give
effect to international law, so international law must be converted or transformed via a separate
law
¨ Pluralist approach = relationship between the two systems. This is more complex and
diverse
effect to international law
→ if you get a question on this, use the words: direct effect and supremacy
In the Netherlands you can rely on provisions from international treaties before national courts,
because the Netherlands has opted for a monist system and therefore the international law
automatically becomes part of the national legal order
→ however, the Netherlands has a moderate monistic system, as only the treaties that are binding for
everyone have direct effect (article 94 Gw)
, Why do we have international law?
• Coexistence = states need to regulate certain issues in order to coexist together. This can’t be
done under national law fully because you can give effect to some rules, but you can’t
regulate how certain things happen. You need to sit with other states and agree to make
certain rules, especially because of the fact that there are a lot of common
threats/opportunities. So, it’s concerned with the basic rules that allow states to exist
peacefully alongside each other
→ international law of coexistence = provides the legal answers to questions that are inherently of
interest to more than one state and is required to separate the powers of the sovereign states and
thereby uphold peaceful coexistence. This law is focuses on the matter in which sovereign states
interact among each other and is therefore primarily horizontal. It merely seeks to ensure that states
can pursue their different and separate issues without disrespecting the sovereignty and rights of other
states. In this case two or more states can have colliding interests in the substantive structure of
international law.
• Cooperation = states can’t coexist without regulating that field of law, but they want to
cooperate. They want to make progress together and therefore they want to regulate certain
issues. So, this goes beyond coexistence to promote collaboration between states in various
areas. It covers areas where states work together to adress common challenges
→ international law on cooperation = provides the legal answers to questions that aren’t inherently
at interest to two or more state but have nevertheless become a matter of international concern
through the adoption of a treaty. It has got to do with the adoption of treaties between States, with
which the issues might be turned into an international matter due to its content
The difference between the international law of coexistence and the international law of cooperation
is that the latter is optional for sovereign States. This means that States can decide for themselves
whether they want to turn matters that were initially governed by national law into a matter of
international law
How does international law work?
You have sovereignty and consent. This means that on the first hand the states have supreme power
over their territory and may not be the subject to the jurisdiction of other state. Moreover, states must
consent to be bound by international rules, without consent they can’t be bound
→ states are considered to be sovereign, so there’s no authority above them. This means that laws can
only be made with their consent and because they’re sovereign they also have the possibility to do this
In international law you don’t have a constitution or a police, so the power is very much horizontally;
states agree to do something together. The absence of an international legal system of enforcement is
characteristic of the international legal order. The lack of a central system means that no central body
can be identified that makes laws/rules. In a national system, the government imposes sanctions when
a legal rule is violated, while in international law, states comply with the rules that result from mutual
agreements, because they consider this to be important and therefore the enforcement lies with the
states themselves. However, sometimes this is done by international organizations, like the UN
