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Customary International Law, Special Custom in International Law, International Law, Asylum Case, Right of Passage Case, Norwegian Fisheries Case, Lotus Case

Subject Categories

Conflict of Laws | Courts | International Law | Law


General customary international law contains rules, norms, and principles that seem applicable to any state and not to a particular state or an exclusive grouping of states. For example, norms relating to the high seas, to airspace and outer space, to diplomatic immunities, to the rules of warfare, and so forth, apply equally to all states having occasion to be concerned with these areas. Similarly, the facts of a given case may suggest exclusively the application of general custom—such as cases concerning collision on the high seas between ships of different countries, cases involving general principles of international law, cases turning on the construction of treaties under general customary canons of construction, and in general cases where the plaintiff and defendant states could theoretically be interchanged with any other states without affecting the content of the rules of law cited by either side in the dispute. By contrast, special customary international law deals with non-generalizable topics such as title to or rights in specific portions of world real estate (e.g., cases of acquisitive prescription, boundary disputes, and so-called international servitudes), or with rules expressly limited to countries of a certain region (such as the law of asylum in Latin America). The line separating general from special custom is similar to that in English common law, where a particular custom "must apply to a definitely limited though indeterminate class of persons" and to a limited geographic area; if the usage is laid in too wide a geographic area, for example, it is taken out of the realm of custom and must be pleaded as an ordinary claim at law.