Knowra Customary international law Customary international law Customary international law consists of rules arising from general state practice accepted as legally obligatory. Its two elements are state practice and opinio juris.
State practice : The conduct of states, including acts, omissions, legislation, diplomatic statements, and official policies. It supplies the observable conduct from which a customary rule may emerge.
Diplomatic immunity : Legal protections that allow diplomatic agents to perform their functions without undue interference by the receiving state. Customary rules on diplomatic relations remain relevant alongside treaty protections.
Treaty : A written agreement governed by international law and concluded between states or other subjects of international law. Treaties derive force from agreement, while custom develops through practice accepted as law.
Francisco de Vitoria : A sixteenth-century Spanish theologian and jurist whose writings addressed relations among peoples and the law of nations. His work helped shape early debates about legal rules governing relations beyond kingdoms.
International Law Commission conclusions on identification of customary international law : A set of 2018 conclusions and commentaries addressing how customary international law is identified. They organize evidence and methods while leaving difficult applications to case-specific analysis.
Opinio juris : The belief that conduct is carried out because international law requires or permits it. It distinguishes legally motivated practice from habit, courtesy, or political choice.
Jurisdictional immunities of the state : Rules limiting when one state’s courts may exercise jurisdiction over another state. The International Court of Justice treated state immunity as grounded in customary law.
General principles of law : Principles recognized across legal systems that international courts may apply as a source of international law. They are a distinct source, not rules established through state practice and opinio juris.
Hugo Grotius : A Dutch jurist whose writings helped systematize early modern European law of nations. His account of the law of nations contributed to later thinking about state practice and legal obligation.
Instant custom : The disputed idea that customary international law can form rapidly from limited practice accompanied by legal acceptance. It tests whether customary rules can emerge without prolonged, widespread conduct.
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