Nov 14, 2020 in Politics

Customary International Law

Customary International Law and Its Norms

Customary international law is a set of developed rules of conduct for international humanitarian law subjects. A custom is an accepted long-established practice formed as a result of repetitive actions and considered by the International Court of Justice as one of the main sources of international legal relations (Cali, 2010). Customary international law is a difficult and controversial subject because the question about its place law in modern legal systems is debatable. A vast majority of countries in the world recognize its principle, although there are many different opinions about what rules and norms it contains. This paper provides a reflection on norms of customary international law and their implementation or violation in the modern world.


Norms of customary international law are so widespread throughout the world that states become bound by them without their ratification. In case of refusal from the implementation of customary norms, they cease to observe such, unless the latter are peremptory or mandatory. The question of the existence of peremptory principles in the system of international law has always aroused a scientific controversy from their complete rejection to unconditional recognition as the basis of international regulations. Jus cogens norms have gained the world recognition of being peremptory norms of the highest status (Cali, 2010). The basis of the concept of jus cogens is that there can be no law higher than human values.

With regard to Basak Calis book International Law for International Relations, I have made a conclusion that all jus cogens norms become principles of customary international law through the approval of states, but not all its rules are at the level of peremptory norms (Cali, 2010). It is significant that jus cogens rules are restrictive, most of which concern the protection of basic human rights, such as freedom from oppression, racial or religious discrimination, and so on. It means that the international community recognizes the inhuman behavior of the state as the most threatening to international peace and security. The importance of the peremptory prohibition of the illegitimate use of force by one country against another should be emphasized. In the traditional sense of legal order, this norm is the most important for its implementation.

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Respect for the territorial integrity of an independent state is a fundamental international law, and without doubt, the aspect of this rule, which forbids aggression against the territorial integrity of a nation, has the status of an imperative norm. It is recognized that the illegal use of force is not only prohibited by the rules indicated in the United Nations Charter and customary international law, but are also contrary to jus cogens or peremptory norms (Cali, 2010). The Commission noted that the prohibition of aggression should be regarded as a mandatory rule. No territorial acquisition arising from the threat or the use of force should be recognized as legal. Thus, according to my opinion, such current event as the Russian annexation of the Crimea is a great violation of the basic part of customary international law, regulating relations between states. Such act is considered illegal and invalid breaching peremptory jus cogens norms.

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Speaking about the relation of customary international law to the use of force against Iraq in 2003 for the anticipatory self-defense purpose, I can tell that in spite of the long-established acceptance of the states right to self-defense, there is a debate that the UN Charter has restricted it to allow a response to a factual military attack only. Under this explanation, the act has replaced the existing right under customary international law to take a rational anticipatory action of self-defense. Thus, according to customary international legal principles, the right of a state to apply force as a warning is a firmly established aspect of the essential human right to self-defense (Cali, 2010).

As I can observe, customary international law has an uncertain status in the American legal system because there is almost no mention of it in the U.S. Constitution. However, American lawyers have noted that the latter does not say anything about whether or not customary international law is part of the American legal system or whether it is a federal law or the one of the states (Cali, 2010). Its provisions do not contain direct guidance for courts when the acts of the Congress or the President come into conflict with the provisions of international treaties and the principles of international rights.

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The most notable expression of the U.S. Supreme Courts opinion concerning the relation of customary international law and the internal legal rules of the country was made in the judgment of the Paquete Habana. During the Spanish-American War, ships of the United States Navy captured fishing vessels, which belonged to Spanish citizens and declared them their war prize. Their owners challenged these actions and asked to return them the ships, arguing that in accordance with international customs, private fishing vessels, even if they belong to the citizens of an enemy state, cannot be subjected to such force actions. Having examined the relevant provisions of international law, the U.S. Supreme Court agreed with the plaintiffs. Based on the judgment above, I can tell that the American legal doctrine recognizes customary international regulations as part of the United States law. However, within its framework, there is no clarity what rights are part of relevant ordinary rules of law, namely, ones of individual states or federal law.

To conclude, as a source of international law, an international custom was altered and acquired different forms in the modern world; however, it is officially recognized by the states as a mandatory rule of law. The qualification of the rules of conduct as customs is a complex process because in contrast to treaty rules, customs are unwritten norms. By their nature, principles of customary international law are a result of the agreement of states. An international custom is a source of law in cases where relations among countries are not regulated by international treaties. Taken together, they form what is called the universal law or universally recognized principles and norms of international law.


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