What international law is, whom it binds, and how it differs from the law of a country

What this chapter is for

This chapter answers the questions that sit under the whole subject. What is international law? Whom does it bind? How is it different from the law of Pakistan, which you already know something about? Every later chapter, on treaties, on the use of force, on the sea or on diplomats, assumes you can answer these in your own words and back each answer with a source.

The chapter has three parts. Sections 1 to 5 build the idea. They start with one ordinary journey that passes through several kinds of law, then give the classic definitions and show how they changed, separate public from private international law, show whom the law binds, and describe the society of states it governs. Sections 6 to 9 show the machinery and set it beside the law of a country. They explain how international law is made, judged and enforced, compare it with national law point by point, map its branches, and show how Pakistan lives with it. Sections 10 to 12 give the critics their say, bring the subject up to date with the Indus Waters award of August 2026, and clear up what students mix up. The last four sections turn all of this into marks.

FPSC asked for this chapter almost word for word in two papers. CE-2016 asked candidates to “Define International Law. Discuss its nature and scope.” CE-2024 asked “In what respects, International law differs from domestic law? Are there any similarities between the two?”¹ Both are answered from what follows.

Before you start

The words

• State. A country in the legal sense: a people living on a territory under a government that answers to no other country. Pakistan, Iran and China are states. Punjab is not, because it answers to the federation.
• Sovereign. Answering to no higher authority. A sovereign state makes its own laws and decides its own affairs.
• Treaty. A written agreement between states (or between states and international organisations) that binds them in law. The UN Charter is a treaty, and so is the Indus Waters Treaty of 1960.
• Custom. A practice that states follow because they believe the law requires it. Many rules of international law were never written down in any treaty and bind all states as custom.
• Municipal law. Lawyers’ name for the law inside a country. Here “municipal” has nothing to do with the city corporation. It means national law, the law of Pakistan or of any other single state. The chapter uses “national law” and “the law of a country” for the same thing.
• Jurisdiction. The power of a court to hear a case, or of a state to make and apply its laws. When a court “has no jurisdiction” it cannot decide the case at all.
• The International Court of Justice (ICJ). The court of the United Nations, which decides disputes between states. It sits in The Hague, in the Netherlands.
• The Security Council. The fifteen-member body of the UN that can order states to act to keep international peace. Five of its members are permanent and can block its decisions with a veto.
• Legal personality. The capacity to have rights and duties under a system of law, and to claim them. A person who has it in international law is called a subject of international law.

The places

Two cities come up again and again. The Hague, in the Netherlands, holds the Peace Palace, where the International Court of Justice and the Permanent Court of Arbitration sit. New York holds the headquarters of the United Nations, where the General Assembly and the Security Council meet. When this book says a dispute “went to The Hague”, it means one of those courts heard it.

The story in plain words

In the early 1600s some London merchants had a claim for money against Philip III, the King of Spain. His ambassador would not pay. On a lawyer’s advice they sued the King in an English court, and the court ordered the sheriffs of London to arrest him if they found him in their area. Philip had nothing to fear from the sheriffs. He did, though, have claims of his own against other English merchants, and while the case stood he could not pursue them. So his ambassador paid.

The philosopher Jeremy Bentham told this story in 1789 to make a point. The merchants and the King had fought their case inside England’s own law. “If the dispute had been betwixt Philip and James himself,” Bentham wrote, meaning the King of Spain against the King of England, “it would have been international.”² That word was new. Bentham coined it for the law that governs the dealings of sovereigns with one another, which until then had been called the law of nations. This chapter is about that law. It asks what it is, who is bound by it, and why it works so differently from the law that sent the sheriffs after a king.

1. One journey, four kinds of law

Start with something ordinary. A family from Lahore flies to Jeddah for Umrah. The trip feels like one thing. In law it passes through at least four separate bodies of rules, and only one of them is the subject of this book.

The passports in their hands were issued by Pakistan under Pakistan’s own law. Once they land, their stay in Makkah is governed by Saudi Arabia’s law, its visa rules, its police and its courts. Each of these is the law of one country, applied by that country’s own officials to the people within its reach.

Suppose a suitcase does not arrive. The airline’s duty to pay for it comes from a treaty on air travel between countries, the Montreal Convention of 1999, wherever that treaty covers the flight. The family does not sue under the treaty directly. Pakistan’s Parliament passed the Carriage by Air Act, 2012 to give the Convention effect, and its schedule sets out the treaty’s rules. Under that schedule the carrier is liable for lost checked baggage if the loss happened while the bag was “in the charge of the carrier”. If a bag has not arrived twenty-one days after it should have, the passenger may treat it as lost.⁸ The rule began as an agreement between states. It reaches the family as an Act of Pakistan’s Parliament, heard in a Pakistani court.

Now suppose a quarrel arises between the two governments themselves. Saudi Arabia, say, accuses Pakistan of breaking an agreement on the treatment of its workers, or Pakistan says Saudi Arabia has mistreated a Pakistani diplomat. No Pakistani court can order Saudi Arabia to do anything, and no Saudi court can order Pakistan. The dispute is between two sovereign states, and the rules that govern it belong to neither of them alone. That is public international law, and it is the only box in Figure 1 that this subject is about.

Two lessons come out of this journey, and the rest of the chapter rests on them. The first is that international law is not a higher layer of the same law that runs Pakistan. It is a different system with its own subjects, its own sources and its own ways of settling disputes. The second is that the two systems touch all the time. A treaty made between states can become part of a country’s law, as the Montreal Convention did, and a country’s laws and courts are often the place where international rules finally reach a person. Chapters 0201 and 0202 take up how the two connect. This chapter keeps them apart long enough to see what each one is.

2. Defining international law

Before Bentham the subject was called the law of nations, a translation of the Latin jus gentium, a Roman term for rules shared by many peoples. Bentham disliked the old name. In his Introduction to the Principles of Morals and Legislation, first published in 1789, he separated two kinds of legal rule by the people they govern. Rules about people who belong to the same state are “internal”. Rules about the dealings of “sovereigns, as such” with one another are “international”. He admitted in a footnote that “The word international, it must be acknowledged, is a new one; though, it is hoped, sufficiently analogous and intelligible.”² He thought “law of nations” was so vague a name that it seemed to describe the law inside a country.

His word caught on. By the early twentieth century the treatise of Lassa Oppenheim, which this section turns to next, used both names for one thing, and said that the subject was “since Bentham, also called ‘International Law’”.³ Your examiners will accept either name. What matters is that both mean the law between states, not the law inside any one of them.

The classic definition comes from Oppenheim, the Whewell Professor of International Law at Cambridge. In the second edition of his treatise, published in 1912, the definition reads:

“Law of Nations or International Law (Droit des gens, Völkerrecht) is the name for the body of customary and conventional rules which are considered legally binding by civilised States in their intercourse with each other.”³

Take it one phrase at a time, because each phrase is a claim. “Customary and conventional rules” names the two sources Oppenheim accepted. Customary rules grow out of how states behave. Conventional rules come from conventions, which is the older word for treaties. “Considered legally binding” separates law from courtesy. States do many things out of politeness, like saluting each other’s warships, without thinking the law requires it. Oppenheim calls that comity and keeps it out of the definition. “By civilised States” limits the law to a club of states that Europe accepted as its equals, a limit the critics in section 10 take apart. “In their intercourse with each other” makes the law about the dealings between states, and nothing else.

Oppenheim drew the consequence in one line that is still the best short description of the subject. Since no sovereign authority stands above the states, the law of nations “is a law between, not above, the several States”.³ Hold on to that phrase. Most of the differences between international law and the law of Pakistan, which section 7 sets out, come from it.

Starke: states, and something more

By the middle of the twentieth century Oppenheim’s definition had become too narrow. The United Nations, the International Labour Organisation and other bodies had rights and duties of their own. The Nuremberg tribunal had punished individuals for crimes under international law. The writer J. G. Starke, who had worked in the legal section of the League of Nations Secretariat, rewrote the definition to take these in. In the second edition of his Introduction to International Law (1950), it reads:

“International law may be defined as that body of law which is composed for its greater part of the principles and rules of conduct which States feel themselves bound to observe, and therefore, do commonly observe in their relations with each other, and which includes also:— (a) the rules of law relating to the functioning of international institutions or organisations, their relations with each other, and their relations with States and individuals; and (b) certain rules of law relating to individuals so far as the rights or duties of such individuals are the concern of the international community.”⁴

Starke kept states at the centre (“for its greater part”). He then added two rings around them, organisations and individuals. He also said why. The older definition, “with its restriction to the conduct of States inter se”, was found in most books written before the Second World War, and “it is not a comprehensive description of all the rules now acknowledged to form part of the subject”.⁴ His phrase “feel themselves bound to observe, and therefore, do commonly observe” makes a second point. States usually keep the rules because they accept them as binding, not because anyone forces them to. That answers, in passing, the charge that a law without a police force is no law, which section 10 returns to.

Compare the two definitions and you see what changed between 1912 and 1950. Oppenheim’s law has one kind of subject, states, and a membership limited to “civilised” ones. Starke’s law has three kinds of subject, states, organisations and individuals, and no test of civilisation. Every state in the world is now bound, the 193 members of the United Nations among them.¹⁷

A good answer quotes one classic definition, says what it got right and what it left out, and then gives its own working definition in plain words. Something like this is enough:

International law is the body of rules, made mainly by states through treaties and custom, that binds states in their relations with one another, and that also governs international organisations and, for some rights and crimes, individuals.

That sentence has three parts, and each one is defended later in this chapter. “Made mainly by states” is section 6. “Binds states” and “also governs organisations and individuals” is section 4. “In their relations with one another” is section 7.

3. Public and private international law

Go back to the lost suitcase. Suppose the bag was booked in Lahore on a Gulf airline, lost in Dubai and claimed in Jeddah. Three countries’ courts might hear the claim, and their laws might give different answers. Which court should hear it, and whose law should it apply? The branch of law that answers questions like these is called private international law, or the conflict of laws.

Despite its name, private international law is mostly national law. Each country has its own rules for deciding which court hears a case with a foreign element, which country’s law applies to it, and whether a foreign judgment will be enforced. Pakistani courts apply Pakistan’s rules on these questions, and English courts apply England’s. The subject is “international” only in the sense that its cases cross borders. Oppenheim was blunt about this. Once Bentham’s division into public and private had been accepted, he wrote, “only the so-called public International Law, which is identical with the Law of Nations, is International Law, whereas the so-called private International Law is not.”³

States do sometimes make treaties to bring their conflict rules into line, and then private international law gains a treaty layer. The body that drafts most of these treaties is the Hague Conference on Private International Law. Pakistan is not a member of the Conference, but it has joined some of its conventions.⁵ It acceded to the Convention on the Civil Aspects of International Child Abduction of 1980 on 22 December 2016, and the Convention came into force for it on 1 March 2017.⁶ This is the treaty under which a parent abroad can seek the return of a child taken to Pakistan by the other parent without consent, and a parent in Pakistan can seek the same in reverse. It works between Pakistan and each country that has accepted Pakistan’s accession. Pakistan also acceded to the Apostille Convention of 1961, which simplifies how a document signed in one country is accepted in another, on 8 July 2022, with effect from 9 March 2023.⁷

When a CSS question says “international law” without a word more, it means public international law, and so does every chapter of this book. Private international law appears in this subject only to be told apart.

4. Whom international law binds

A legal system has to say whose rights and duties it governs. The law of Pakistan governs citizens, companies, government departments and so on. International law answers the same question differently, and its answer has grown over the last eighty years. The three rings of Figure 2 are the answer in its present form.

States are the first subjects of international law and still its main ones. They make it, they are bound by it, and only they can bring or answer a case in the world’s main court. The Statute of the International Court of Justice says so in one sentence: “Only states may be parties in cases before the Court.”⁹ When Pakistan sued India over the shooting down of a Pakistani aircraft in 1999, both parties were states. So were both parties in the case India brought against Pakistan over Kulbhushan Jadhav, decided in 2019. Chapter 0301 sets out what makes an entity a state, and chapter 0304 covers the full list of subjects.

The second ring took a death to establish. On 17 September 1948 Count Folke Bernadotte, the United Nations Mediator for Palestine, was murdered in Jerusalem.²³ Could the UN itself claim compensation for harm done to it and to its agents, as a state can for harm to its citizens? Only states had ever brought international claims. The General Assembly asked the International Court of Justice for its opinion.

The Court answered in 1949 that it could. It reasoned from what the UN Charter set the organisation up to do. The Charter gave the UN rights and duties distinct from those of its members and charged it with keeping international peace. In the words of the UN’s summary of the opinion, the Court concluded that the Organization “has at the same time a large measure of international personality and the capacity to operate upon an international plane, although it is certainly not a super-State.”¹⁰ Note both halves. The UN is a subject of international law with real rights, including the right to bring a claim against a state for harm to its agents. It is not a world government, and it is not the equal of a state in every respect.

The third ring is the individual. For most of its history international law treated people as objects. A state could complain if another state mistreated its citizen, but the citizen had no rights of their own. Two changes after 1945 made the individual a subject for some purposes.

The first was criminal. At Nuremberg the defence of the leaders of Nazi Germany argued that international law “is concerned with the action of sovereign States, and provides no punishment for individuals”. The International Military Tribunal rejected the argument in its judgment of 1946: “Crimes against international law are committed by men, not by abstract entities, and only by punishing individuals who commit such crimes can the provisions of international law be enforced.”¹¹ Individuals can now be tried for genocide, crimes against humanity and war crimes, which chapter 1304 covers.

The second was the law of human rights, which gives individuals rights against states, including their own state. Chapter 1302 covers it. This is the change Starke built into the second half of his definition in 1950, when he wrote of rules for individuals “so far as the rights or duties of such individuals are the concern of the international community”.⁴

Keep the limits in view. An individual still cannot sue a state in the International Court of Justice. Most of a person’s rights under international law reach them only through a treaty body, a regional court, or their own country’s courts. The individual is a subject for some purposes and an object for the rest.

5. The society international law governs

Every legal system belongs to some community. The law of Pakistan governs the people of Pakistan, and the rules of a cricket board govern its clubs. Oppenheim made this the first test of whether something is law at all. He defined law as “a body of rules for human conduct within a community which by common consent of this community shall be enforced by external power”.³ So before asking whether international law is real law, ask a simpler question. Is there a community of states for it to govern?

Oppenheim answered yes, and his reasons still hold. No country can produce everything its people need, so states trade. Trade needs ships, railways, posts and telegraphs that cross borders, and all of these need agreed rules. States keep envoys and consuls in each other’s capitals to handle the daily traffic of business between governments. They had set up international offices and, in 1899, a Permanent Court of Arbitration at The Hague. The states are sovereign and no government stands above them, he wrote, “yet there is something mightier than all the powerful separating factors: namely, the common interests.” Those interests bind the states into one community, which “for many hundreds of years” had been called the Family of Nations or the Society of Nations.³ He also saw its great gap. In 1912 the society “entirely lacks at present any organisation whatever”, and he looked to the Hague Peace Conferences as the first traces of one.³

Oppenheim’s society was a club with a door, and Europe kept the key. Its first members were the Christian states of Western Europe. The states of the Americas joined next. The Ottoman Empire was admitted by Article 7 of the Peace Treaty of Paris of 1856, and Japan after its rise at the end of the nineteenth century. Persia, Siam and China, though they made treaties and kept envoys, were in his view still only partly inside.³ The critics in section 10 judge what this says about where the law came from.

The society today is universal. All 193 members of the United Nations belong to it, from China to Tuvalu, along with the organisations they have created.¹⁷ It now has the organisation Oppenheim was waiting for. There is a General Assembly where every member votes, a Security Council, a standing world court and a family of specialised agencies. It still has no government above the states, and that is the key to everything that follows. The society is held together by the thing Oppenheim named, the common interests of its members.

Those interests explain why a society with no ruler produces law that is mostly kept. Take the rules on diplomats. Pakistan keeps embassies in scores of capitals, and scores of countries keep embassies in Islamabad. Every one of those states is both a sender and a receiver of envoys. If Pakistan arrested a foreign ambassador today, its own ambassadors would be at risk tomorrow. So each state keeps the rule because it needs others to keep it too. Lawyers call this reciprocity. It is the reason a horizontal order, which section 7 sets beside the vertical order of a country, can work at all.

6. How the law is made, judged and enforced

Every legal system has to answer three questions. Who makes the law? Who decides what it means in a dispute? Who makes people obey it? Inside Pakistan the answers are Parliament, the courts and the executive with its police. International law answers all three differently, and the differences explain most of what is strange about it.

Take the first question, who makes the law. No parliament sits above the world’s states. The rules are made by the states that are bound by them, in two main ways. A treaty binds the states that join it, and only them. Pakistan is bound by the Indus Waters Treaty because it signed and ratified it. A rule of custom binds all states, with narrow exceptions that chapter 0205 explains. It is formed when states generally follow a practice because they believe the law requires it. Article 38 of the Statute of the International Court of Justice lists what the Court applies. These are treaties, custom, “the general principles of law recognized by civilized nations”, and, as a secondary help, judicial decisions and the writings of the best-qualified jurists.⁹ Chapter 0203 explains the list, and chapters 0204 to 0209 take each source in turn.

The rule that holds the treaty system together is in the Vienna Convention on the Law of Treaties of 1969: “Every treaty in force is binding upon the parties to it and must be performed by them in good faith.”¹² Lawyers call it by its Latin name, pacta sunt servanda, agreements must be kept.

The second question is who judges. Inside Pakistan, if someone sues you, you must answer in court whether you like it or not. Between states, a court can decide a dispute only if both states have agreed to its jurisdiction. They can agree for one case, in a treaty clause covering a whole class of disputes, or in a declaration accepting the Court’s jurisdiction in advance. Article 36 of the Court’s Statute lays out these routes.⁹

Pakistan learned this rule at its own cost. After India shot down a Pakistani aircraft on 10 August 1999, Pakistan took India to the International Court of Justice. It relied on the declarations by which both states had accepted the Court’s jurisdiction. India’s declaration of 1974, though, excluded disputes with any member of the Commonwealth, and Pakistan is one. The Court held that India could rely on that reservation and found, by fourteen votes to two, that it had no jurisdiction.¹³ The Court never decided whether the shooting was lawful. It had no power to.

The third question, who enforces, has the most surprising answer. No world police force exists to make a state obey a judgment. The UN Charter does contain two strong promises. Each member “undertakes to comply with the decision of the International Court of Justice in any case to which it is a party”. If a party fails to, the other “may have recourse to the Security Council”, which may recommend or decide on measures to give effect to the judgment.¹⁴ Members also “agree to accept and carry out the decisions of the Security Council”.¹⁴ The Council can order sanctions and, in the last resort, the use of force. Yet its five permanent members each hold a veto, so it cannot act against any of them, or against a state one of them protects.

Most of the time, then, international law is enforced in other ways. A state that breaks a rule may face retaliation from the state it wronged, the loss of the benefits of the treaty it broke, or damage to its standing with other states it needs. Most of all, states keep the rules because they want other states to keep them too. Chapter 0106 sets out these ways in full, and chapter 0107 asks how well they work.

7. International law and the law of a country, point by point

CE-2024 asked how international law differs from domestic law and whether there are any similarities.¹ This section answers both halves. Begin with the picture.

Inside a country, law runs downward. A body above the citizens makes it, a court hears every case brought within its jurisdiction, and officials can arrest, fine and seize. Lawyers call this a vertical order. Between states nothing stands above them. The same states that are bound by the law make it, so the order is horizontal. Oppenheim put the result in one sentence a century ago: “the Law of Nations is a law not above, but between Sovereign States, and therefore a weaker law.”³ The UN Charter writes the same idea into its first principle: “The Organization is based on the principle of the sovereign equality of all its Members.”¹⁴

Oppenheim listed three differences between the two systems. They differ in their sources, in the relations they regulate, and in the substance of their law, since one is the law of a sovereign over its subjects and the other a law between sovereigns.³ A modern answer keeps his three and adds what more than a century of practice has shown. Set out side by side, they are these.

Each row is a point for an answer, and each can be backed with a source from this chapter. The first and fourth rows rest on Article 38 and Article 36 of the Court’s Statute.⁹ The second rests on the Reparation opinion and the Nuremberg judgment.¹⁰¹¹ The fifth rests on Articles 25 and 94 of the Charter.¹⁴ The last row needs a word of explanation. International law has no constitution sitting above everything else. A small group of rules, such as the ban on genocide, are treated as overriding any treaty that conflicts with them, and chapter 0207 explains them.

One more difference catches many states out. Inside a country, a later law can change an earlier one, and the government follows whatever the law of the land now says. In international law, a state cannot use its own law as an excuse. The Vienna Convention says: “A party may not invoke the provisions of its internal law as justification for its failure to perform a treaty.”¹² A state that passes a law contrary to its treaty is still in breach of the treaty.

The similarities

The second half of the CE-2024 question is the one most candidates skip, and it is where an answer can rise above the rest. The two systems have more in common than the table suggests.

Both are systems of rules that those bound by them accept as binding, not as advice. This is the point of Starke’s phrase about rules “which States feel themselves bound to observe, and therefore, do commonly observe”.⁴ Both make rules in two broad ways, by deliberate enactment (statutes in a country, treaties between states) and by long practice (custom in both). Both are applied by courts that reason in the same lawyerly way, reading texts, following earlier decisions and weighing evidence. The two even share part of their content. Article 38 tells the International Court of Justice to apply “the general principles of law recognized by civilized nations”, meaning principles found across the world’s national legal systems, such as good faith and the rule that no one should be judge in their own cause.⁹

The strongest similarity is that the two now work together. Much of international law reaches people through national law. The Montreal Convention reaches a passenger through the Carriage by Air Act, 2012.⁸ The Vienna Conventions on diplomatic and consular relations reach Pakistan’s courts through the Diplomatic and Consular Privileges Act, 1972, whose section 2 gives them “the force of law in Pakistan”.¹⁵ A judgment of the International Court of Justice against Pakistan was carried out by an Act of Pakistan’s Parliament, as section 9 shows. A good answer ends on this point. The two systems differ in structure, but each depends on the other.

8. The branches of the subject

What does international law cover? This is the “scope” that CE-2016 asked about.¹ Its answer is a map of the subject, and FPSC’s syllabus is that map. Its seventeen heads fall into eight branches, as Figure 4 shows.

Read the map from the top. The first branch is about the system itself, its nature and basis (head I), and its sources and its relation to national law (head II). The second is about who acts in it: states and their recognition (III), international organisations (VIII), and what happens when one state replaces another (XII). The third covers how states make agreements and settle disputes: treaties (IV) and peaceful settlement, including the International Court of Justice (V).

The next four branches cover what states may and must do. Territory, the sea, the air and outer space (IX) cover where a state’s power runs. The responsibility of states for wrongs (X), their jurisdiction over people and events (XI), and the law of diplomats and consuls (XV) cover the powers and duties of states towards each other. The individual (XIII) covers nationality, human rights, refugees and international crimes. Money and resources (XIV) cover trade, investment and the environment.

The last branch is the oldest, force and war. It covers the rules on when a state may use force (VII), the rules of conduct once fighting starts (VI), the older law of war and hostilities (XVI), and neutrality (XVII). For three centuries this branch was the heart of the subject. The great change of the twentieth century was that the other seven grew around it, until most of international law came to concern peace.

When an examiner asks for the “scope” of international law, these eight branches are the answer. Name them, give one example of each, and say that the subject has grown from a law of war and diplomacy into a law that touches trade, the environment, human rights and the individual.

9. Pakistan and international law

Pakistan has lived with international law since the day it was born, and its record is a good set of cases for any answer. Five points cover it.

Pakistan’s own Constitution looks outward. Among the Principles of Policy, Article 40 says the State shall “promote international peace and security, foster goodwill and friendly relations among all nations and encourage the settlement of international disputes by peaceful means”.¹⁶ The Fourth Schedule gives the Federation power over “External affairs; the implementing of treaties and agreements, including educational and cultural pacts and agreements, with other countries; extradition”, and over “International treaties, conventions and agreements and International arbitration”.¹⁶ So in Pakistan, treaties are a federal matter, and a treaty usually reaches Pakistan’s courts only after Parliament has made it law.

Pakistan joined the system at once. It became a member of the United Nations on 30 September 1947, seven weeks after independence.¹⁷ It has been elected to the Security Council eight times, most recently for 2025 and 2026.¹⁸

Pakistan makes treaties part of its own law by Act of Parliament. The Carriage by Air Act, 2012, the Diplomatic and Consular Privileges Act, 1972 and the Pakistan Maritime Zones Act, 2023 each give a treaty force inside Pakistan.⁸¹⁵²⁴ Chapter 0201 explains why Pakistan, like Britain, needs such an Act before a treaty binds its courts.

Pakistan has used the Court and been bound by it. It lost on jurisdiction in the Aerial Incident case of 2000, as section 6 showed.¹³ In the Jadhav case India sued Pakistan over Kulbhushan Jadhav, an Indian national whom Pakistan had detained and a military court had convicted. Pakistan’s case was that he had crossed into Pakistan on a genuine passport in a false name to carry out espionage and terrorist activities.¹⁹ The Court held in 2019 that Pakistan had breached Article 36 of the Vienna Convention on Consular Relations, which entitles a detained foreigner’s own country to be told and to visit him. It refused India’s requests to annul the conviction and to order his release. It found that Pakistan was “under an obligation to provide, by means of its own choosing, effective review and reconsideration of the conviction and sentence of Mr. Jadhav”, if necessary by “enacting appropriate legislation”.¹⁹ Pakistan did so. Parliament passed the International Court of Justice (Review and Re-consideration) Act, 2021, which lets a foreign national, or a consular officer of their country, petition a High Court to review a military court’s conviction where consular access was denied.²⁰ That is the whole of this chapter in one case. A rule made by treaty between states, applied by an international court on the consent both states gave in a treaty, carried out by the national Parliament of the state that lost.

Pakistan relies on international law in its largest disputes. On Kashmir, Pakistan’s position rests on the Security Council’s resolutions, which in the Foreign Office’s words provide that the final disposition of the state “will be made in accordance with the will of the Kashmiri people expressed through the democratic method of a free and impartial plebiscite conducted under the auspices of the United Nations”.²⁵ Chapter 0302 sets the dispute out. On the Indus, it rests on a treaty and the courts that treaty created, as section 11 shows. A state in Pakistan’s position, smaller than its main rival and dependent on rivers that rise outside its borders, has more reason than most to want the rules kept.

10. The critics

International law has been doubted from the start. Three criticisms come up in the papers. Answer each one fairly, and then reply to it.

The oldest criticism, that it is not law at all, comes from the English jurist John Austin in the nineteenth century. Oppenheim summarised it this way. Austin and his followers “define law as a body of rules for human conduct set and enforced by a sovereign political authority.” By that definition, international law cannot be law, because no sovereign stands over the states.³ CE-2023 quoted Austin’s conclusion that “International Law is no law, it is only positive morality”, meaning a set of moral rules backed only by opinion.¹

Oppenheim’s reply is still a good one. Law needs a community, rules of conduct within it, and a common consent that the rules will be enforced by some outside power. It does not need a sovereign or a parliament. States do agree that the law of nations shall be enforced, and in the absence of a central authority they enforce it themselves, by self-help and by the help of other states. That makes international law weaker than national law, but “a weak law is nevertheless still law”.³ A modern answer adds the practice. States argue in legal terms, appoint legal advisers, defend themselves in courts and pass Acts like Pakistan’s 2021 Act to carry out judgments. They do not treat the rules as mere morality. Chapter 0109 takes this debate in full.

The second criticism is that international law is Europe’s law, made for Europe. It comes from the states that were colonised. Read Oppenheim’s own words and the point makes itself. He wrote in 1912 that international law “is in its origin essentially a product of Christian civilisation”. A new state, to be admitted to what he called the Family of Nations, had to be “a civilised State”, and the existing members had to consent to its entry. Persia, Siam, China and others, though “certainly civilised States”, were in his view not yet full members.³ The rules on colonies, on the acquisition of territory and on the protection of foreign investors were written by the powers that held empires.

The reply is that the newly independent states did not walk away from international law. They joined it and changed it. They used their votes in the General Assembly to condemn colonial rule and to claim lasting sovereignty over their natural resources, and they helped to write the modern law of the sea. The “civilised states” test disappeared from the definition, as Starke’s version shows. Chapter 0103 tells this story, and chapter 0110 asks what remains of the criticism.

The third criticism is that the strong obey international law when it suits them and ignore it when it does not. The veto keeps the five permanent members of the Security Council beyond its enforcement. Powerful states have used force without the Council’s approval and faced no penalty.

There is truth in this, and an answer should say so in measured words. Yet the strong also need the rules, for their trade, their aircraft, their diplomats and their citizens abroad. Most rules are kept most of the time. A weaker state like Pakistan gains more from the rules than a stronger one, because the rules are its protection when power is not on its side. The Indus Waters case in the next section is an example.

11. Where international law stands now

The clearest recent case of international law at work for Pakistan is the dispute over the Indus Waters Treaty. Chapter 0407 tells the whole story. Here it serves to show the features of the subject that this chapter has taught.

On 23 April 2025, after an attack by armed men in the part of Jammu and Kashmir that India holds, India announced that “[t]he Indus Waters Treaty of 1960 will be held in abeyance with immediate effect, until Pakistan credibly and irrevocably abjures its support for cross-border terrorism”.²¹ Those are India’s words. The Treaty, signed in 1960 with the World Bank’s help, divides the rivers of the Indus basin between the two countries. It also has its own procedure for disputes, which lets either party take a dispute to a Court of Arbitration. Pakistan had started such a case in 2016 over the design of India’s hydro-electric plants.

The Court of Arbitration first held, on 27 June 2025, that India’s announcement could not limit its power to hear the case. Its competence could not be affected by “the unilateral actions of a Party after the start of the arbitral proceedings”. On 31 August 2026 it went further. In a unanimous award, it found that “abeyance” is not used in the Treaty and “has no technical meaning in international law”. It then examined each ground on which India could claim to suspend or end the Treaty and found that none applied. It held that “there is no rule allowing a State to unilaterally terminate or suspend the operation of a treaty based on its ‘sovereignty’“. India’s decision was “not permissible”, and the Treaty “remains fully in force”.²¹ India did not take part in this phase of the proceedings. The Court took India’s positions into account as far as it could find them in India’s public statements and letters.²¹

Pakistan’s Deputy Prime Minister and Foreign Minister, Muhammad Ishaq Dar, welcomed the award the same day. “The Award vindicates Pakistan’s consistent position that a binding international treaty cannot be unilaterally suspended or set aside. India must fully comply with its obligations under the Treaty and with the binding decisions of its dispute settlement mechanisms.”²²

Look at the case through this chapter. The parties are two states, and the law between them is a treaty both agreed to (section 4). The Court could act because both had consented to it in advance, in the Treaty itself (section 6). India’s claim of sovereignty could not change the Treaty, because agreements must be kept. That rule is written into the Vienna Convention and binds every state as custom, whether or not it has joined the Convention (sections 6 and 7). No police force exists to make India comply. The award’s force rests on India’s treaty promise, on the standing of a unanimous international court, and on the weight other states give it (section 6 again). Every strength and every weakness of international law is visible in one dispute.

Pakistan is also, for 2025 and 2026, one of the ten elected members of the Security Council.¹⁸ It is helping to apply, from the inside, the system whose rules it relies on.

12. What students mix up

“Municipal law” means the law of a city. It does not. In international law, municipal law is the whole law of a country, from its Constitution down. The law of Pakistan is municipal law in this sense.

Private international law is a branch of international law. It is mostly national law. Each country has its own rules on which court hears a case with a foreign element and which law applies. Treaties like the Child Abduction Convention harmonise some of them, but the subject is not the law between states.

International law binds only states. That was Oppenheim’s view in 1912. Since the Reparation opinion of 1949 international organisations have legal personality, and since Nuremberg individuals can be punished for international crimes.¹⁰¹¹ States remain the main subjects, but not the only ones.

The International Court of Justice can hear any dispute between states. It can hear only a dispute both states have consented to. The Aerial Incident case of 2000 failed on exactly this point.¹³

A treaty Pakistan has signed is automatically law in Pakistan’s courts. It binds Pakistan in international law once Pakistan has ratified it. As a rule, a Pakistani court applies it only once Parliament has made it law, as with the Carriage by Air Act. Chapter 0201 explains why.

Since there is no world police, international law is not enforced. It is enforced differently, by the Security Council in some cases, by retaliation and the loss of treaty benefits, by national courts and legislatures, and above all by states’ wish to have others keep the rules. Calling it weaker is fair. Calling it unenforced is wrong.

Bentham defined international law. Bentham coined the word in 1789. The classic definitions come from Oppenheim (second edition, 1912) and Starke (second edition, 1950).

13. What the examiners have asked

In the eleven papers from CE-2016 to CE-2026, two questions sit squarely on this chapter’s ground.¹

• CE-2016, Q2. “Define International Law. Discuss its nature and scope. To what extent it is relevant and effective in the modern times?” (20 marks)
• CE-2024, Q5. “(a) Is International law a law or positive morality? Give reasons to support your answer. (b) In what respects, International law differs from domestic law? Are there any similarities between the two?” (20 marks)

Both questions join this chapter to its neighbours. The CE-2016 question’s last part is the subject of chapter 0107, on effectiveness, and part (a) of the CE-2024 question is the subject of chapter 0109, on why international law binds. CE-2023 also quoted Austin’s charge that international law is “only positive morality”.¹ Expect this chapter to be the opening of an answer far more often than the whole of one. Almost any question on the nature of the subject needs the definitions and the comparison taught here.

14. Facts to carry into the hall

• Jeremy Bentham coined the word “international” in An Introduction to the Principles of Morals and Legislation, first published in 1789, for the law of “the mutual transactions between sovereigns”.²
• Oppenheim (2nd edition, 1912): international law is “the body of customary and conventional rules which are considered legally binding by civilised States in their intercourse with each other”. It is “a law between, not above, the several States”.³
• Starke (2nd edition, 1950) added rules on international organisations and “certain rules of law relating to individuals”.⁴
• Reparation for Injuries, advisory opinion of 11 April 1949: the UN has “a large measure of international personality”, but “is certainly not a super-State”.¹⁰
• Nuremberg, 1946: “Crimes against international law are committed by men, not by abstract entities”.¹¹
• ICJ Statute, Article 34(1): “Only states may be parties in cases before the Court.” Article 38(1) lists the sources the Court applies.⁹
• UN Charter, Article 2(1): sovereign equality. Article 25: members carry out Security Council decisions. Article 94: members comply with judgments of the Court.¹⁴
• Vienna Convention on the Law of Treaties, Article 26 (pacta sunt servanda) and Article 27 (internal law is no excuse).¹²
• Pakistan: UN member since 30 September 1947. Elected to the Security Council eight times, most recently for 2025 and 2026.¹⁷¹⁸
• Constitution of Pakistan, Article 40 (peaceful settlement of international disputes). Fourth Schedule, entries 3 and 32 (external affairs, treaties, international arbitration).¹⁶
• Aerial Incident (Pakistan v. India), 21 June 2000: no jurisdiction, fourteen votes to two.¹³ Jadhav (India v. Pakistan), 17 July 2019: effective review and reconsideration. Carried out by the International Court of Justice (Review and Re-consideration) Act, 2021.¹⁹²⁰
• Indus Waters Western Rivers Arbitration, award of 31 August 2026, unanimous: the Treaty “remains fully in force”.²¹

15. What loses marks on this topic

• A definition with no source. “International law is the law between nations” earns little. Name Oppenheim or Starke, quote the key phrase, and say what it shows.
• Stopping at the definition. The CE-2016 question also asked for nature and scope. Nature is the horizontal order of section 7. Scope is the eight branches of section 8. Leave either out and you have answered a third of the question.
• Answering only the differences. CE-2024 asked for similarities too. An answer that lists six differences and no similarity has dropped part of the marks before it starts.
• Calling the UN a world government. The Court itself said it “is certainly not a super-State”.¹⁰
• Treating Austin’s view as the last word. A question that quotes Austin wants you to weigh him, not repeat him. Give his view, then Oppenheim’s reply and the evidence of practice, then your own judgment.
• Writing Pakistan’s cases loosely. Pakistan did not “lose the Aerial Incident case on the merits”. The Court found it had no jurisdiction and never reached the merits. Precision with your own country’s cases is where an examiner sees whether you know the subject.

16. A worked answer plan

Take part (b) of CE-2024, Q5: “In what respects, International law differs from domestic law? Are there any similarities between the two?” Suppose you give it half the question’s time, about seventeen minutes, for ten marks.

Opening (three or four sentences). International law and domestic law are both systems of binding rules, but they are built differently. Domestic law is made, applied and enforced by bodies that stand above the people it binds. International law is made by the same sovereign states it binds and has no legislature, compulsory court or police above them. In Oppenheim’s phrase, it is “a law between, not above,” the states. The two differ in structure but share their nature as law, and today they work through each other.

The differences (five points, each with its source).

1. Makers. Parliament, against states making law by treaty and custom (ICJ Statute, Article 38).
2. Subjects. Everyone in the jurisdiction, against states first, then organisations (Reparation, 1949) and individuals (Nuremberg, 1946).
3. Consent. A statute binds all, against a treaty binding only its parties.
4. Courts. Compulsory jurisdiction, against consent (Article 36). Use Aerial Incident, 2000.
5. Enforcement. Police and courts, against self-help and the Security Council (Charter Articles 25 and 94), with the limit of the veto.

The similarities (three points).

1. Both are accepted as binding by those they bind. Use Starke’s “feel themselves bound to observe, and therefore, do commonly observe”.
2. Both make rules by enactment and by custom, and both are applied by courts reasoning in the same way. They share general principles (Article 38(1)(c)).
3. They now work together. Treaties reach people through Acts such as the Carriage by Air Act, 2012, and an ICJ judgment was carried out by Pakistan’s Act of 2021 after Jadhav.

Judgment (two or three sentences). The differences are real and come from one fact, the absence of any authority above sovereign states. They make international law a weaker law, not a lesser kind of law. Pakistan’s own record, as a litigant at The Hague and as a state that turns treaties and judgments into its own Acts, shows the two systems as partners rather than rivals.

Why this plan and not another. The question has two parts, and the plan gives each its own heading so the examiner sees both answered. Each difference carries a source, and the similarities end on Pakistan’s practice, which no textbook answer has. A common wrong answer lists eight differences from memory, adds one line saying “both are law”, and stops. It loses most of the marks for the second half.

What to remember from this chapter

• International law is the law between states. Bentham named it in 1789. Oppenheim defined it as the rules “considered legally binding by civilised States in their intercourse with each other”, and Starke widened it to take in organisations and individuals.
• Private international law is a different subject. It decides which court and which country’s law apply to a private case that crosses a border, and it is mostly national law.
• States are the main subjects of international law. International organisations have personality since Reparation (1949), and individuals can be punished for international crimes since Nuremberg (1946).
• The law is made by the states it binds, judged only with their consent, and enforced without a police force. That is why it is horizontal where national law is vertical.
• The two systems differ in makers, subjects, consent, courts and enforcement. They are alike in being binding rules made by enactment and custom and applied by courts, and they now work through each other.
• The syllabus’s seventeen heads fall into eight branches, from the system itself to force and war. That map is the “scope” of the subject.
• Pakistan joined the UN on 30 September 1947, has sat on the Security Council eight times, gives treaties force by Act of Parliament, and carried out the Jadhav judgment by an Act of 2021.

Check yourself

1. In Bentham’s story of the London merchants and the King of Spain, why was the case “internal” and not “international”?

2. Name two things Oppenheim’s definition of 1912 included that a modern definition drops or changes, and say why.

3. A student writes: “Private international law is the part of international law that deals with individuals.” Correct the sentence.

4. Why did the International Court of Justice not decide whether India acted lawfully in shooting down a Pakistani aircraft in August 1999?

5. Give one similarity between international law and the law of Pakistan, and support it with a Pakistani example.

6. Plan, in five lines, an answer to CE-2016, Q2: “Define International Law. Discuss its nature and scope.” Leave out the last part, on effectiveness.

7. In the Indus Waters award of 31 August 2026, what did the Court of Arbitration say about India’s claim to hold the Treaty “in abeyance”? Which rule of this chapter does the award illustrate?

8. From the chapter on how to sit this paper: you want to use the Aerial Incident case in an answer. What do you write in the hall to cite it, and what single point from it do you make in an answer on how international courts get their power?