According to the ontological stance adopted in this essay, a concept is a mental representation. It is the generalized idea of an empirical or normative phenomenon or state of affairs or a class of such phenomena or state of affairs. This essay is concerned with a specific category of concepts typically referred to as “concepts of international or international law” or “international legal concepts.” International legal concepts figure prominently in the way international lawyers think and talk about international law. This raises questions about their possible function or functions. Arguably, international legal concepts would not be used on such a large scale if they did not also fill important needs. What exactly are those needs? What does international legal discourse need legal concepts for? The Danish professor Alf Ross wrote on this topic in the beginning of the 1950’s. As he observed, the function of legal concepts is intimately connected with their role as meddling links or connectives in legal inferences. This observation led Ross to the conclusion that legal concepts serve to economize the expression of law in verbal form. As I will argue, by reason of their role as meddling links in legal inferences exactly, legal concepts serve a number of other functions as well. To substantiate my argument, in this essay I will illustrate the “camouflaging,” “normative,” “disclosing,” “systemizing,” and “formative” functions of legal concepts in international legal discourse.