Customary international law

How it is used

It has two elements: state practice and 'opinio juris', the belief that the practice is legally required. It binds states even without a treaty. Lawyers and diplomats argue about whether a rule 'has become' or 'reflects' customary international law.

Example sentences

1. Many rules on diplomatic immunity were part of customary international law long before 1961.

2. The court found that the rule reflects customary international law.

3. Even states that have not ratified the treaty are bound by customary international law.

Common collocations

• rule of customary international law
• state practice
• opinio juris
• reflect customary international law

Related terms

• international lawThe body of rules that governs relations between states and other international actors, based mainly on treaties, custom and general principles of law.
• treatyA formal written agreement between states, or between states and international organisations, that is governed by international law and creates legal obligations.
• International Court of JusticeThe main judicial organ of the United Nations, based in The Hague, which settles legal disputes between states and gives advisory opinions on questions of international law.
• bindingCreating a legal obligation that the parties must follow, so that a binding agreement or decision cannot simply be ignored.

More terms: International Law & Human Rights

• human rights
• territorial integrity
• self-determination
• recognition
• refugee
• asylum
• non-intervention