Legal Definitions - operative performance bond

Opinio Juris Sive Necessitatis

Opinio Juris Sive Necessitatis is a fundamental concept in international law that refers to the belief by states that a particular practice is legally obligatory. For a consistent and widespread practice among nations to evolve into a rule of customary international law, it is not enough that states simply follow the practice; they must also do so out of a genuine sense of legal duty, rather than merely out of convenience, political expediency, or moral conviction. This belief in legal obligation is what distinguishes a customary international law from a mere habit, courtesy, or political act among nations.

• Example 1: Protection of Civilian Aircraft in Peacetime

  Imagine a scenario where, for decades, no nation has intentionally shot down a civilian airliner belonging to another country during peacetime, even in moments of high international tension. This consistent practice is widely observed. For this practice to become a rule of customary international law, it's not enough that states simply avoid shooting down planes; they must also believe they are *legally prohibited* from doing so under international law. If a nation were to shoot down a civilian airliner and other nations universally condemned it, not just as an immoral act, but as a clear violation of international law, this would demonstrate the existence of opinio juris sive necessitatis, solidifying the practice as a binding legal norm.

• Example 2: Granting Immunity to Visiting Heads of State

  When a head of state visits another country, it is a common practice for the host nation to grant them diplomatic immunity from local prosecution. While many treaties address diplomatic immunity, the broader principle of immunity for heads of state is also considered customary international law. This is because nations not only consistently grant such immunity but also do so out of a belief that they are *legally obligated* to respect the sovereignty and status of the visiting head of state under international law. If a country were to arrest a visiting head of state for a minor local offense, other nations would likely protest, citing a breach of international legal custom, thereby affirming the existence of opinio juris sive necessitatis.

• Example 3: Prohibition of Torture

  The prohibition of torture is a widely accepted norm in international law. While numerous treaties explicitly ban torture, it is also considered a rule of customary international law, binding even on states that have not ratified specific anti-torture conventions. This is because states not only generally refrain from torture but also universally acknowledge that they are *legally bound* by international law to do so. The global condemnation of torture, not just as an unethical act but as a violation of fundamental international legal principles, reflects the strong opinio juris sive necessitatis that underpins its status as a peremptory norm (jus cogens) of international law.