The decisions of international and municipal tribunals and the publications of scholars cannot be used as a source of law as such, but as a means of recognizing the law established in other sources. In practice, the International Court of Justice does not refer to national decisions, although it relies on its previous jurisprudence. When considering State practice in determining the relevant rules of international law, it is necessary to take into account any activities of State organs and officials relating to that purpose. There has been an ongoing debate about how to make a difference in terms of the weight that should be given to what states do, rather than what they say is the law. In its most extreme form, this would mean rejecting what states say as a practice and banning it as evidence of opinio juris.  A more moderate version would assess what a state is saying in relation to the time the statement was made.  Only relatively powerful countries with many international contacts and interests regularly have the opportunity to contribute to the practice of international law through action. The main means of State practice for the majority of States will be to participate in meetings of international organizations, in particular the General Assembly of the United Nations, by voting and otherwise expressing their views on the issues under consideration. Moreover, there are circumstances in which what States say may be the only evidence of their views on the conduct required in a particular situation.  The importance of general principles has undoubtedly been diminished by the increasing intensity of contractual and institutional relations between States.
Nevertheless, the concepts of confiscation and equity have been used in the settlement of international disputes. For example, a State which, by its conduct, has encouraged another State to believe in the existence of a particular legal or factual situation and to rely on that belief may be prevented from asserting a contrary situation in its actions.  The principle of good faith has been described by the ICJ as “one of the basic principles for the creation and performance of legal obligations.”  Similarly, reference has often been made to fairness.  There is general agreement that fairness cannot be used to undermine legal rules (i.e., operate contra legem).  This notion of “justice as a right” is reinforced by references to the principles of fairness in the text of the 1982 United Nations Convention on the Law of the Sea, although this may be little more than an admission of the existence and legitimacy of the arbitrator`s discretion. Sources of international law include international practices (general state practice accepted as law), treaties and general principles of law recognized by most national legal systems. International law can also be reflected in the international community, the practices and customs of states to maintain good relations and mutual recognition, such as.B. patronage under the flag of a foreign ship or the enforcement of a decision of a foreign court. 2 S. Guggenheim (Lehrbuch des Völkerrechts, Bd. I, S.
48), with reference to Max Huber, the term “common international law” refers to norms valid throughout the space field of international law, but is of the view that they also include norms that were not created by customs. However, a peculiarity of international humanitarian law is that some of its rules govern armed conflicts between a State and an armed opposition group or between such groups. The rules governing such conflicts apply to all parties, whether a State or an armed opposition group. Analysis of State practice shows that many rules of international humanitarian law applicable in non-international armed conflicts are binding on both States and armed opposition groups. A mandatory norm or ius cogens (Latin for “imperative law” or “strong law”) is a principle of international law that is considered so fundamental that it prevails over all other sources of international law, including the Charter of the United Nations. The principle of ius cogens is enshrined in article 53 of the Vienna Convention on the Law of Treaties: both contract law and customary international law are sources of international law. Treaties, such as the four Geneva Conventions of 1949, are written conventions in which states formally establish certain rules. Treaties are binding only on States that have expressed their consent to be bound by them, usually by ratification. A number of States attach importance to the principle of territorial sovereignty and therefore regard States as free in their internal affairs. Other States reject this view.
A group of opponents of this view, including many European nations, argues that certain norms of behavior are expected of all civilized nations, including the prohibition of genocide, slavery and the slave trade, wars of aggression, torture and piracy, and that the violation of these universal norms constitutes a crime, not just against individual victims. but against humanity as a whole. States and individuals who subscribe to this view are of the view that the person responsible for the violation of international law “like the pirate and slave trader before him hostis humani generis, has become an enemy of all humanity” and is therefore prosecuted in a fair trial before any fundamentally just court. through the exercise of universal jurisdiction. Ancient Greece, which developed the basic notions of governance and international relations, contributed to the formation of the international legal system; Many of the first recorded peace treaties were concluded between Greek city-states or with neighbouring states. The Roman Empire created an early conceptual framework for international law, jus gentium (“law of nations”), which regulated both the status of foreigners living in Rome and the relations between foreigners and Roman citizens. Adopting the Greek concept of natural law, the Romans understood ius gentiumas as universal. However, unlike modern international law, Roman international law applied to relations with and between foreign individuals rather than between political entities such as states.
International law establishes the framework and criteria for identifying States as key actors in the international legal system. Since the existence of a State presupposes control and jurisdiction over the territory, international law deals with the acquisition of territory, the immunity of States and the legal responsibility of States in their conduct among themselves. .