customary international law

Article 38(1)(b) of the ICJ Statute refers to “international custom, as evidence of a general practice accepted as law”. Two elements are needed: state practice that is extensive and virtually uniform, including the practice of specially affected states; and opinio juris, the belief that the practice is legally required. Practice without that belief is mere usage or courtesy.

Custom binds all states, except a persistent objector who consistently objected while the rule was forming. A rule of custom may exist alongside an identical treaty rule. In India, customary rules are part of domestic law so far as they do not conflict with an Act of Parliament.

Example

Though India is not a party to the treaty, the rule binds it as customary international law because state practice and opinio juris both support it.

In Indian law

• Article 38(1)(b), Statute of the International Court of Justice
• North Sea Continental Shelf cases (ICJ, 1969) and Nicaragua v. United States (ICJ, 1986): state practice and opinio juris
• Gramophone Co. of India Ltd. v. Birendra Bahadur Pandey, 1984 INSC 40: customary international law applies in India unless in conflict with statute

See also

opinio juris · jus cogens · treaty · monism

Read more in the study notes

• Introduction to the law of evidence and its central conceptions (Bharatiya Sakshya Adhiniyam)
• Article 370 and special provisions for States (Constitutional Law II)
• Absolute liability, polluter pays and the precautionary principle (Environmental Law)
• Sustainable development and the Stockholm, Rio and Johannesburg Declarations (Environmental Law)
• Application of Hindu law: who is a Hindu (Family Law I - Hindu Law)
• Origin and development of human rights (Human Rights Law and Practice)