Customary International Humanitarian Law

Customary International Humanitarian Law
Name	Customary International Humanitarian Law
Jurisdiction	International law
Formed	19th–21st centuries
Related	International humanitarian law, Geneva Conventions, Hague Conventions

Customary International Humanitarian Law is the body of unwritten rules emerging from general practice accepted as law that governs conduct during armed conflict and supplements treaties such as the Geneva Conventions and the Hague Conventions. It has evolved through state conduct in episodes including the Franco-Prussian War, the First World War, the Spanish Civil War, the Second World War, and more recent conflicts like the Yugoslav Wars, the Gulf War, and the Syrian Civil War. Customary rules inform adjudication in bodies such as the International Court of Justice, the International Criminal Court, and domestic tribunals including the Nuremberg Trials and the International Criminal Tribunal for the Former Yugoslavia.

Definition and Nature

Customary International Humanitarian Law comprises norms derived from the practice of states such as United States, United Kingdom, France, Russia, China and regional actors like European Union members and non-state participants like Hezbollah and Taliban when their conduct is widely observed, combined with opinio juris as expressed in decisions of the International Court of Justice, the International Criminal Tribunal for Rwanda, advisory opinions of the International Law Commission, and writings by scholars such as Henckaerts and Doswald-Beck. It is distinct from treaty obligations found in instruments like the Additional Protocol I to the Geneva Conventions and instruments like the Rome Statute but overlaps where customary rules codify treaty provisions upheld by institutions such as the International Committee of the Red Cross and adjudicated by the European Court of Human Rights. Customary norms can be erga omnes in effect in adjudications involving parties such as Israel, Iraq, Afghanistan, and adjudicators like the Special Tribunal for Lebanon.

Sources and Formation

Sources include the general practice of states evidenced in diplomatic correspondence from capitals such as Washington, D.C., London, Paris, and Moscow; military manuals from institutions like the United States Department of Defense and the Ministry of Defence (United Kingdom); judicial decisions by courts including the International Criminal Tribunal for the Former Yugoslavia and the International Criminal Court; resolutions and reports of the United Nations Security Council, the United Nations General Assembly, and commissions such as the Stremlau Commission. Formation also relies on treaties like the Geneva Conventions and the Hague Regulations where widespread practice reflects opinio juris, and scholarly restatements such as the ICRC’s study and the International Law Commission's work. Practice by armed forces in operations named Operation Desert Storm, Operation Enduring Freedom, and Operation Iraqi Freedom contributed to the crystallization of rules on conduct such as targeting and detention.

Identification Methodology

Identification employs methods used by the International Court of Justice, the International Criminal Court, and the International Law Commission, combining evidence of consistent state practice—examples include official manuals from Israel Defense Forces, the French Armed Forces, the Russian Ground Forces—with expressions of legal conviction (opinio juris) found in instruments from the United Nations, judgments from the European Court of Human Rights, and scholarship by jurists like Martti Koskenniemi and Michael Walzer. Fact-finders analyze military orders, diplomatic notes, declarations by heads of state such as Barack Obama or Vladimir Putin, and policy statements by organizations such as the NATO or the African Union. Methodology was refined in landmark cases like the Nicaragua v. United States decision and in compilations like the ICRC Customary IHL study.

Core Rules and Doctrines

Core customary rules include the principles of distinction and proportionality articulated in cases before the International Court of Justice and reflected in the Geneva Conventions, protections for civilians in sieges such as during the Siege of Sarajevo, prohibitions on certain weapons as seen in actions involving Cluster munitions and doctrines applied in judgments involving Bosnia and Herzegovina and Rwanda. Doctrines include humane treatment of detainees as in the Gulf War detention practices reviewed by the European Court of Human Rights, prohibition of indiscriminate attacks in operations like NATO bombing of Yugoslavia, and protections for medical personnel symbolized by the Red Cross and the Red Crescent. Customary norms also address perfidy, neutrality, and combatant status issues as litigated in proceedings like the Hamdan v. Rumsfeld case and discussed by the International Committee of the Red Cross.

Applicability and Legal Effects

Customary international humanitarian norms bind states and relevant non-state parties such as the Provisional IRA or insurgent groups in the Colombian conflict insofar as practice and opinio juris exist, and they are applied by courts including the International Criminal Court, the Special Court for Sierra Leone, and national courts in South Africa and France. Violations can result in individual criminal responsibility adjudicated by tribunals like the Nuremberg Tribunal precedent and state responsibility assessed by the International Court of Justice. Legal effects include obligations to prevent, prosecute, and provide remedies; interaction with sanctions adopted by the United Nations Security Council; and customary constraints on conduct in operations such as Operation Allied Force.

Relationship with Treaty Law

Customary rules interact with treaties such as the Geneva Conventions, the Hague Conventions, Additional Protocol I, and the Rome Statute through complementary, supplementary, or independent application: treaties may codify existing custom as in the Geneva Conventions adoption, while jurists debate whether provisions of Additional Protocol I attained customary status. The International Court of Justice and the International Criminal Tribunal for the Former Yugoslavia have adjudicated overlaps between treaties and custom, and states such as United States, China, and India have made declarations addressing whether treaty provisions reflect customary obligations.

State and Non-State Actor Practice

State practice is documented in military manuals from United States Army, the French Army, the Russian Ministry of Defence, and legislative acts of parliaments like the British Parliament and United States Congress; non-state practice appears in communiqués by actors such as FARC, ISIS, Hezbollah, and the Kosovo Liberation Army. International organizations including the United Nations, NATO, the African Union, and the European Union shape practice through operations and policy, while advocacy groups such as Human Rights Watch and Amnesty International record adherence and violations. This corpus of conduct, decisions, and commentary informs tribunals like the Special Tribunal for Lebanon and domestic courts in states including Israel and Lebanon regarding the existence and scope of customary norms.

Category:International law