Nature, basis and history of international law

International Law · Nature and sources. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.

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The idea

Public international law is the body of rules that binds states and other international persons, such as international organisations, in their relations with one another. Private international law (conflict of laws) is different: it is part of each country's own law and decides which court and which national law deal with a private dispute that has a foreign element.

There is no world legislature or police, so writers ask why the law binds. The natural law school says the rules come from reason and justice. Positivists say they come from the consent of states, shown in treaties and custom. Grotius joined both ideas; Oppenheim is the standard positivist.

Rules to remember

Jeremy Bentham coined the term 'international law' in 1789.
Hugo Grotius, De Jure Belli ac Pacis (1625): called the father of international law; Mare Liberum (1609) argued for the freedom of the seas.
Peace of Westphalia (1648): usual starting point of the modern system of sovereign, equal states.
Natural law: rules are found by reason and bind whatever states will.
Positivism (Oppenheim, International Law, 1905-06): the law rests on the common consent of states.
John Austin: international law is only 'positive international morality' because no sovereign commands and enforces it.
Weak point of pure consent theory: new states are bound by custom that existed before them.

Common mistake

Students treat private international law as a branch of international law between states. It is national law about private disputes with a foreign element; only public international law governs relations between states.

Worked example

A French woman and a Pakistani man married in Dubai ask a court in Karachi to end their marriage. The court must first decide whose divorce law applies. Which branch of law answers this?

The parties are private persons, not states or international organisations.
The dispute has foreign elements: a foreign spouse and a marriage made abroad.
Choosing the applicable national law is the task of the conflict of laws, which each country lays down in its own legal system.

Answer: Private international law (conflict of laws), not public international law.

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Sources: Article 38 of the ICJ Statute →Take a International Law test