This article is devoted to current practices concerning the application of general principles of law in the light of their function in the international legal system. As a means of the application and interpretation of both treaty and customary law, general principles of law perform a crucial function in the system of international law, which is understood as set of interrelated rules and principles – norms. The role played by general principles of law in the international legal order has been discussed by academia for years now. Initially they were used to ensure the completeness of the system of international law. However, at the current stage of development of international law, when many of them have been codified, they are usually invoked by international courts for the interpretation of treaties and customary law and/or the determination of their scope. This means that despite their ongoing codification they do not lose their character as general principles and are still applied by international courts in the process of judicial argumentation and the interpretation of other norms to which they are pertinent. References by international courts to general principles of law perform the allimportant function of maintaining the coherence of the international legal order, which is faced with the twin challenges of fragmentation and the proliferation of international courts.
International law reflects systemic conditions compatible with its essence, which means that a space must exist inside the borders of that order for the presence of the phenomenon of general principles. The assumption that international law is a legal system ipso facto means that general principles must exist within its borders. A general principle of law is a necessary element of every legal order. It is a form and a tool in which the efforts of the individual seeking to comprehend a given phenomenon are materialized through imposing order on it rather than by breaking it down into unconnected and independent elements. Since law is an expression of order, law therefore applies general principles. The systematicity of law, and therefore of international law as well, creates the primary source of the binding force of any norm. Considerations of natural law or positive law justifications for the presence of general principles in international law are of little consequence, as the source of general principles is the systemic nature of the law. Order and hierarchy are part of the rationalized system in which norms of law present themselves. This dependency applies also to norms of international law. The role of the judge is to fill in the appropriate normative content (general principles) in fields constituting at one and the same time both a necessary element and a consequence of the systemic character of the international legal order. Within this context the principle of good faith constitutes one of the bases for considerations concerning the extent of the international legal order. The extent of international law reaches as far as the extent to which evidence of good faith are present among the subjects of international law. The impossibility of describing relations between two states by the use of the determinants of good faith, translated in turn into a normative general principle, determinates the limits of international law.
This article discusses the classical question whether general principles of law form a separate source of international law. To this end it adopts the method of a posteriori analysis, examining the normative nature of various principles of law one by one. This analysis leads to the conclusion that only some principles have a normative nature, while others lack it.
There are different meanings and functions of what is called a “general principle of law.” This article seeks to address their importance as the basis for the systemic integration of the international legal order. When international law is considered as a legal system, its normative unity and completeness seems essential. This article argues that general principles of law are a necessary, although less visible, element of international legal practice and reasoning, which secure the systemic integration and long-lasting underpinnings of international law. In this sense they may be seen as the gentle guardians of international law as a legal system.