What is international law?
International law (also called public international law or the law of nations) is the set of rules that states accept as binding on each other. It also covers international organisations such as the UN, and, more and more, the rights and duties of individuals.
It is different from national (municipal) law, which a country's own parliament makes for people inside it.
- There is no world parliament: states make the rules by agreeing to them.
- There is no world police: rules are enforced by reciprocity (I keep my promise so you keep yours), reputation, sanctions, courts and, in rare cases, the UN Security Council.
- States are sovereign (they rule themselves) and have sovereign equality: big or small, each has the same legal rights.
Regional law can go further. In a regional union of states (for example the European Union), common institutions make rules that apply directly inside member countries and take priority over national law in those areas.
A short history
- Ancient times: treaties and rules about envoys existed in ancient India, Mesopotamia, Egypt, Greece, Rome and China. Indian texts discussed fair conduct in war and the safety of messengers.
- 1625: the Dutch scholar Hugo Grotius wrote a famous book on the law of war and peace.
- 1648: the Peace of Westphalia in Europe set the idea of equal, sovereign states.
- 1864–1907: the first Geneva Convention (care for the wounded) and the Hague Conferences (rules of war, peaceful settlement).
- 1919: the League of Nations, the first world body for peace. It failed to stop the Second World War.
- 1945: the UN Charter: no use of force except self-defence or Security Council action; the International Court of Justice is created.
- 1948 onwards: the Universal Declaration of Human Rights, the Geneva Conventions of 1949, decolonisation, the law of the sea (1982), international criminal courts (1998).
Sources of international law
The statute of the International Court of Justice (Article 38) lists the sources the court uses:
- Treaties (conventions, charters, agreements): written promises between states. They bind only the states that agree to them. Steps: negotiate → sign → ratify (formal approval at home) → enter into force. The key rule is pacta sunt servanda: agreements must be kept.
- Customary international law: rules shown by (a) general and consistent state practice and (b) opinio juris, the belief that the practice is legally required. Custom binds almost all states, even without a treaty. Example: diplomatic immunity.
- General principles of law found in most legal systems, such as good faith, fairness and that whoever causes harm must repair it.
- Helpers (subsidiary means): judicial decisions and the writings of leading experts, used to find and explain the rules.
Some rules are so basic that no state may break them by treaty. They are called jus cogens (for example the bans on genocide, slavery and torture). UN General Assembly resolutions are usually not binding, but they can show or help create custom.
The UN, the International Court and human rights
The United Nations (1945, 193 member states) aims to keep peace, develop friendly relations and protect human rights.
- General Assembly: every member has one vote.
- Security Council: 15 members (5 permanent, with a veto). It can make binding decisions on threats to peace, including sanctions.
- International Court of Justice (ICJ): in The Hague, 15 judges. It settles disputes between states that accept its jurisdiction and gives advisory opinions.
International human rights law protects every person from abuse by states: the Universal Declaration (1948), and binding treaties such as the two Covenants of 1966 on civil and political rights and on economic, social and cultural rights, and conventions on the rights of the child, against torture and against discrimination.
International humanitarian law (the law of armed conflict, mainly the Geneva Conventions) limits how wars are fought: protect civilians, the wounded and prisoners; no weapons that cause needless suffering. The International Criminal Court can try individuals for genocide, crimes against humanity and war crimes.
Settling international disputes
The UN Charter says states must settle disputes peacefully. The main ways, from least to most formal:
- Negotiation: the states talk directly.
- Good offices and mediation: a third party helps them talk or suggests a solution.
- Inquiry and conciliation: experts find the facts or propose terms.
- Arbitration: the states choose judges (arbitrators) and agree to obey the decision (award).
- Judicial settlement: a permanent court, such as the ICJ or the law-of-the-sea tribunal, gives a binding judgment.
Regional bodies and the World Trade Organization (for trade disputes) also help. Force is allowed only in self-defence against an armed attack or with Security Council approval.
International law and national (municipal) law; India
How does a treaty become part of a country's own law?
- Monism: international and national law form one system. A ratified treaty applies directly in courts (for example, in the Netherlands and, for many treaties, France).
- Dualism: they are two separate systems. A treaty needs a national law to apply inside the country (for example, the UK and India).
India: Article 51 of the Constitution asks the state to promote international peace and respect international law and treaties. Article 253 lets Parliament make laws to carry out treaties, even on subjects normally left to the states. Indian courts read Indian law in harmony with international law when there is no conflict, and have used human-rights treaties to fill gaps. India was a founding member of the UN, has served many times on the Security Council and is among the largest providers of UN peacekeepers.
Key formulas and definitions
- Main sources: treaties, custom, general principles; helpers: court decisions, expert writings
- Custom = state practice + opinio juris (sense of legal duty)
- Pacta sunt servanda: treaties must be kept
- Treaty steps: negotiate → sign → ratify → enter into force
- Disputes: negotiation → mediation → arbitration → court
- Monism: treaty applies directly; dualism: needs a national act
Worked examples
1. Two neighbouring states disagree about fishing rights. They ask a respected third state to help them talk. Which method is this?
Mediation (or good offices). The third party helps, but its suggestions are not binding.
2. For centuries all states have refused to arrest foreign ambassadors, believing they must not. What source of law is this?
Customary international law: long state practice + opinio juris. It was later written into the 1961 Vienna Convention on Diplomatic Relations.
3. State A never signed a treaty banning a certain fishing net. Is it bound by that treaty?
No. A treaty binds only parties. But if the same rule has become customary law, State A may be bound by the custom.
4. India signs and ratifies a treaty on protecting the sea. Can an Indian court apply it directly to punish a polluter?
India is mostly dualist, so a punishing rule usually needs an Act of Parliament (Article 253 allows this). Courts can still use the treaty to interpret Indian law.
Common mistakes
- Thinking the UN is a world government. It has no power to make laws for all people; states remain sovereign.
- Thinking a treaty binds every state. It binds only the states that agreed to it (custom can bind more widely).
- Mixing up the ICJ and the International Criminal Court. The ICJ settles disputes between states; the ICC tries individual persons for the worst crimes.
- Thinking international law has no effect because there is no world police. Most states obey most rules most of the time, because of reciprocity, reputation and trade.