In addition to treaties, rules of IHL can also be found in customary law. Such rules are established by way of repetitive and uniform practice of States involved in armed conflicts or of third States concerning armed conflicts, in the belief that the behaviour that is practiced is obligatory.
Two elements are considered in determining the existence of customary law: practice and opinio iuris. Practice refers to State conduct that is consistent (but not necessarily absolutely uniform) over time. Opinio iuris is a subjective element, i.e., the belief that that specific pattern of action is required by law.
In the field of IHL, examples of practice include expressions in official statements, military manuals and can also be found in allegations of violations by one state against another state, or in defences against violations. Such practice is particularly relevant because not all States are involved in armed conflicts, and therefore their practice related to IHL will be more readily found in statements and military manuals. In addition, in the case of belligerents, it is difficult to determine the battlefield practice and whether it is accompanied by opinio iuris.
In determining the existence of customary IHL, recourse is had to the practice and opinio juris of States. Whether the practice and opinio juris of other types of actors - such as non-state armed groups, international tribunals and international organizations - may also contribute to custom is controversial.
See Treaties;
OUTLINE
DOCUMENTS
CASES
- ECtHR, Milanović v. Croatia
- ICRC, CIHL
- ICJ, Nuclear Weapons Advisory Opinion (paras 66, 82)
- Sweden, Report on the Swedish IHL Committee
- Case No. 77, United States, President Rejects Protocol I
- Israel, Cheikh Obeid et al. v. Ministry of Security
- Israel, Cases Concerning Deportation Orders (paras 4-7)
- ICJ, Nicaragua v. United States (paras 174-178, 181, 185, 186 and 218)
- Sudan, Report of the UN Commission of Enquiry in Darfur (paras 156-165)
- South Africa, Sagarius and Others
- South Africa, S v. Petane
- ICTY, The Prosecutor v. Tadic (A. para 99)
- ICTY, The Prosecutor v. Kupreskic et al. (paras 527-534 and 540)
- Colombia, Constitutional Conformity of Protocol II (paras 6-10)
- European Court of Human Rights, Kononov v. Latvia
- United Kingdom, The Case of Serdar Mohammed (Court of Appeal and Supreme Court Judgments)
- Central African Republic/Democratic Republic of Congo/Uganda, LRA attacks
- Central African Republic, Coup d'Etat
- Colombia, Special Jurisdiction for Peace, Extrajudicial Executions in Casanare