This law of reason is called by him as Natural Law. Hall and Lawrence consider international law to be a true law. According to them, international law derives from custom and precedent, which are a source of law, and is usually treated as a certain type of positive law. Nor can the absolute concept of sovereignty be reconciled with the Charter of the United Nations, which recognizes the principle of “sovereign equality” in Article 2, the same provision that sets out other cornerstones for the post-war order, such as the peaceful settlement of disputes and the prohibition of the use of force.
As a matter of positive international law in force today, States are not fully sovereign ie,. In particular, they are not free to develop a set of rules governing the use of force that contravenes the prohibition of the Charter of the United Nations, nor do they have any legal means of circumventing such rules by withdrawing their consent. The same can be said for other fundamental principles and norms, such as self-determination and human rights. Sources of international law include international custom (general state practice is accepted as law), treaties and general principles of law recognized by most domestic legal systems.
In considering responses to a particular international situation, States often consider relevant international laws. Neither of the two main sources of international law identified there, customary international law and treaties, has an obvious counterpart in domestic law. Democracies in the developing world, because of their past colonial histories, often insist on non-interference in their internal affairs, particularly with regard to human rights norms or their peculiar institutions, but they often strongly support international law at the bilateral and multilateral levels, as in the United Nations, and especially with regard to the use of force, disarmament obligations and the terms of the Charter of the United Nations. At the international level, although international organizations exercise some functions that are normally associated with States, traditionally only States have been described as sovereign.
In the modern era, Dutch naturalist lawyer Hugo Grotius is credited with laying the foundations for the emergence of international law as a genuine system of positive law, rather than simply a source of universal moral principles or “natural law”. This value consists of certainty, predictability and a sense of common purpose in international affairs that derives from the existence of a set of rules accepted by all international actors. In some cases, domestic courts may rule against a foreign State (the realm of private international law) for an injury, although this is a complicated area of law where international law intersects with domestic law. It also includes the important functions of the maintenance of international peace and security, arms control, the peaceful settlement of disputes and the regulation of the use of force in international relations.
For better understanding, emphasis has also been placed on the difference between international law and domestic law and the sources of international law. International law establishes the framework and criteria for identifying States as the main actors in the international legal system. The first is that, unlike ordinary citizens in national legal systems that are contrasted with officials, States in the international legal order are both subjects of international law and their officials (their creators,. Many people now see the nation-state as the principal unit of international affairs, and believe that only States can choose to voluntarily enter into commitments under international law, and that they have the right to follow their own advice when it comes to the interpretation of their commitments.
National law can become international law when treaties allow national jurisdiction to supranational tribunals such as the European Court of Human Rights or the International Criminal Court. A stronger international legal order followed, supported by institutions such as the International Court of Justice and the United Nations Security Council, and by multilateral agreements such as the Genocide Convention. The International Law Commission (ILC) was established in 1947 to help develop, codify and strengthen international law. .