International Law

What rules are there in your family? Are they the same as the rules in your best friends' families? What if all those families found themselves stranded together on a desert island? Eventually, they'd have to come up with a common set of rules they could all agree to, to prevent major fallouts. International law is that set of rules, but for all the countries of the world.

International Law International Law

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Table of contents

    In this article, we are going to explore the history of international law, we'll look at different types of international law and explore a couple of examples.

    International law definition

    International law is a growing and evolving body of rules, norms, and conventions that define what is acceptable behaviour between sovereign states. It aims to standardise, organise international relations to attain humanity's most important goals. It, therefore, applies to themes such as war, diplomacy, trade, environmental protection and human rights.

    It generally applies to nations rather than individuals, but it can also apply to international organisations such as the European Union.

    International law is not binding but is based on the concept of “agreement must be kept”, from the Latin pacta sunt servanda. Countries typically abide by it through consent in the knowledge that doing so is mutually beneficial, and not doing so, may lead to economic, diplomatic, or military consequences.

    A sovereign state is a political entity with a centralised government that has recognised authority over its territory

    International law is an evolving body of rules and historical norms which are supposed to be observed by all nations to organise and stabilise international relations.

    The International Court of Justice (ICJ) is the United Nations body that supports countries to settle disputes based on international law. For the ICJ to have jurisdiction over a dispute, all countries involved have to consent to it.

    The ICJ does not have the power of enforcement: it cannot make countries do what international law suggests they should. If consenting countries do not abide by the recommendations of the ICJ, then the case will go to the United Nations Security Council for enforcement.

    International law is based on international treaties, individual countries' general practice that translates into international customs, and general legal principles.

    TreatyAlso called a protocol, convention or pact, it's an international, legally binding agreement between states or international organisations. For example, The United Nations Charter.
    International customsA continued general practice, accepted as law. For example, granting immunity for visiting heads of state.
    General legal principlesThese are basic, abstract, shared principles that can provide guidelines for judges when deciding on individual cases. For example, the principle of equality of sovereign states.

    History of international law

    The history of international law goes as far back as the history of the written word. Also, as societies are constantly changing, so are the norms that regulate international behaviour.

    Let's have a closer look.

    Ancient International Law

    Early forms of international law were created as soon as different, independent states emerged within regions of the world. A good example of ancient international law is the Egyptian and the Hittite peace treaty.

    Egyptian and the Hittite Peace Treaty

    International Law The Egyptian version of the Kadesh treaty on the temple of Karnak, Luxor, Egypt StudySmarter

    Fig. 1 The Egyptian version of the Kadesh treaty on the temple of Karnak, Luxor, Egypt

    International Law Part of the Hittite clay tablet of the Kadesh treaty written in Akkadian from 1269 BCE held in Istanbul Turkey StudySmarterFig. 2 Part of the Hittite clay tablet of the Kadesh treaty written in Akkadian from 1269 BCE held in Istanbul Turkey

    Here we can see the Egyptian and the Hittite written versions of the Treaty of Kadesh dating to 1258 BCE. It is one of the few ancient treaties where both sides were found and therefore can be compared. The two ancient powers pledge peace and alliance. They promise, overseen by the respective Gods, to no longer dispute, to recognise each other's borders and to support each other in case of invasion or internal uprising.

    We have examples of rules regarding war, the treatment of neutral parties, the observation of borders, the treatment of foreigners and international conduct from Ancient Greece (from 1200 BCE), the Roman Empire (from 625 BCE), China (from 1570 BCE), and the ancient Indian Subcontinent (from 1500 BCE).

    Natural and Positive Law

    The Ancient Greeks introduced the concept of natural law, which is one of the bases of modern international law. Natural law is the concept that underpins laws created from the observation of human nature. These laws are based on the common humanity and equality between all people, on which depend their intrinsic universal rights.

    Examples of natural law are the laws on violence and murder.

    Natural law stands in opposition to positive law, which includes laws, only valid in specific nations and at specific times in history, imposed on people from society and the state.

    Examples of positive law are highway legislation or drinking-age laws.

    In terms of the origin of international humanitarian law, we look at the ancient Islamic world. In the 7th Century C.E. the Caliphate institutionalised behaviours necessary to limit military damage and the treatment of prisoners of war.

    During the Middle Ages, (500-1500 C.E.) the principles of natural law were bound with religious principles and applied to relations between states. International law was mainly concerned with defining “just war”.

    Modern international law

    Several historical events catalysed the modern development of international law.

    • The development of the printing press (1440).
    • The arrival of Greek thinkers to Europe following the fall of the Byzantine Empire (1453).

    • The emergence of the concepts of natural rights such as life and liberty in the Enlightenment (from the 17th century)

    • The consolidation of European states.

    The Dutch lawyer Hugo Grotius (1583-1645) is considered one of the fathers of international law. He understood international relations to be governed by laws, customs and mutual agreements rather than force and warfare.

    Grotius secularised International law in his work On the Law of War and Peace1 and articulated the principles of natural law that all countries could agree on independently of local customs and differences.

    He also inspired the two schools of thought on international law: the naturalists, who prioritise natural law, and the positivists, who prioritise positive law.

    International Law Portrait of Hugo Grotius StudySmarterFig. 3 Portrait of Hugo Grotius

    The Westphalian system

    The Peace of Westphalia was a key historical event in the modern development of international law.

    The Peace of Westphalia is the name given to two peace treaties signed in 1648 which ended two major wars and brought peace to the Holy Roman Empire.

    It lead to what was retrospectively named the Westphalian system. It was a system that recognised equality between, and national sovereignty of existing nation-states. The Westphalian system also cemented the principle of inviolability of a nation's borders and secured acceptance and tolerance for religious choices.

    Following the Peace of Westphalia, nations became richer and more complex and started developing codified legal systems where naturalists and positivist principles were merged and synthesised.

    European colonisation (starting in the 16th century) spread the concept of sovereignty to many parts of the world.

    Sovereignty is the authority of a state over itself.

    20th Century Developments in International Law

    The creation of the United Nations (1945) following the 2 world wars exemplified a further attempt to further the principles of international law.

    The United Nations Charter contains the principles of state sovereignty, international cooperation, non-intervention and collective security.

    International law became even more “international” when, following the process of decolonisation (started in the 1960s), many newly independent states could take part in, and influence international law.

    The recent process of globalisation means social, cultural, economic, political and diplomatic interactions between states are part of everyday life.

    Since the United Nations was formed, many other organisations such as the World Health Organisation have emerged to regulate, support and moderate international interactions.

    Types of international law

    The body of International law can be subdivided into public and private international law and supranational law.

    Public international law

    Public international law coincides with the current definition of International law. It's the body of norms that standardises and regulates behaviour between countries.

    Public international law includes, among others, the law of the sea, humanitarian law, international criminal law, human rights law and refugee law.

    Private International law

    Private international law, also called “conflict of laws” refers to the discrepancies between international law and countries' own laws, also called municipal law. It regulates which body of law has jurisdiction when an internal case has an international or foreign element.

    Private international law exists because the activities of private individuals go beyond the borders of their county of nationality. For example, private international law will deal with a cross-country divorce settlement.

    Supranational law

    Supranational law covers the legislation of a regional or international body that individual countries sign up for. By doing so, the countries explicitly give up their right to make judicial decisions.

    Judicial decision: the decisions made by a court.

    The European Union (EU) is one of the world's most prominent international organisations that uses a supranational legal framework. The European Court of Justice has supremacy over all the individual countries' courts when it comes to applying EU law.

    International law human rights

    International human rights law is the body of law intended to promote and ensure the observance of human rights everywhere.

    International human rights law is mainly constituted by treaties and international customs.

    The Universal Declaration of Human Rights (1948) is a United Nations declaration that enshrines human rights. It is not binding, but it is used as a base for international human rights instruments.

    International human rights instruments are treaties and other international documents that international human rights law and the protection of human rights are based on.

    Examples of international human rights instruments are the Convention on the Elimination of all Forms of Discrimination Against Women (1981) and the Convention of the Rights of Persons with Disabilities (2008)

    To protect and promote human rights in specific regions of the world, international human rights law is supplemented by regional systems.

    There are three main regional human rights instruments:

    • The African Charter on Human and People's rights (1986).

    • The American Convention on Human Rights (1978).

    • The European Convention on Human Rights (1953).

    The enforcement of human rights law is the responsibility of individual states, as there is no international human rights court. There are, however, regional courts such as the European Court of Human rights and the Inter-American Court of Human Rights which enforce human rights law in their respective regions. Also, the International Criminal Court hasn't got specific jurisdiction over human rights but does cover matters of genocide and crimes against humanity.

    International law examples

    A good example of how the international community can work together to regulate behaviour and benefit al is International environmental law.

    International environmental law is the body of law that represents the world's collective effort to solve the main environmental problems that face humanity today (for example global warming and the mass extinction of wildlife) while achieving sustainable development. Sustainable development means maintaining a high quality of life today without compromising future generations' quality of life.

    International cooperation between countries often means a level of sacrifice for individual countries. This makes International environmental law “worth” it when there is a collective benefit, and only necessary when the problem to solve crosses national boundaries, such as air or water pollution; or is caused by international actions, such as the international of elephant ivory.

    Then, International environmental law takes the form of binding treaties or non-binding agreements. One of the main international organisations coordinating and promoting international environmental law is the UN. Presently there are no bodies that can enforce international environmental law, however regional courts and the International Court of Justice have a degree of jurisdiction on the matter.

    International Law - Key takeaways

    • International law is an evolving body of rules and historical norms which are supposed to be observed by all nations to organise and stabilise international relations.
    • Principles of international law date back to antiquity, as they emerged as soon as sovereign states did.
    • Hugo Grotius is one of the fathers of international law due to his articulation of the principles of natural law that all countries could agree on independently of local customs and differences.
    • The two schools of thought on international law are the naturalists and the positivists.
    • The Peace of Westphalia was a key historical event in the development of international law, as it set out a system that recognised equality between and national sovereignty of nation-states.
    • The types of international law are public, private, and supranational.
    • Examples of international law are international human rights law and international environmental law.


    1. Hugo Grotius De Jure Belli ac Pacis, On the Law of War and Peace 1625
    2. Fig. 1 The Egyptian version of the Kadesh treaty on the temple of Karnak, Luxor, Egypt ( by Olaf Tausch ( licenced by CC-BY-3.0 ( on Wikimedia Commons
    3. Fig. 2 Part of the Hittite clay tablet of the Kadesh treaty written in Akkadian from 1269 BCE held in Istanbul Turkey (,_written_in_Akkadian._1269_BCE._From_Bo%C4%9Fazk%C3%B6y,_Turkey._Clay_tablet._Museum_of_the_Ancient_Orient,_Istanbul,_Turkey.jpg)by Osama Shukir Muhammed Amin FRCP(Glasg)( licenced by CC-BY-SA_4.0 ( on Wikimedia Commons
    Frequently Asked Questions about International Law

    How is international law enforced? 

    Some kind of international law can be enforced through the UN Security Council.

    What is an example of international law? 

    International environmental law and international human rights law.

    What is international law in simple terms? 

    International law is an evolving body of rules and historical norms which are supposed to be observed by all nations to organise and stabilise international relations. 

    What is the role of international law? 

    The role of international law is to set standards for international behaviour among states and international organisations.

    What is international law based on? 

    International law is based on international treaties, international customs, and general legal principles. 

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