The relations existing in the various states of the world, and particularly in the various states of Europe and America, between international law and municipal law, or, as it might better be called, national law, have been made the subject of several studies in recent years. In view of the probable necessity for many years yet to come of relying for the development and application of international law upon national legislatures, courts, and executive or administrative officials, in the absence of any adequate system of international legislatures, courts, and executive officials, this borderland between international law and national law deserves the most thorough attention. But the attention given to the way in which international law is enforced by national courts, the way in which international treaties are supplemented by national statutes, and to other similar phases of the general subject, has led to some neglect of the central question in the problem, or, at least, has not afforded an adequate answer to that question. It is the purpose of this paper to state this question as it has arisen in cases tried in American courts, to attempt to find the proper solution for it, and to compare that solution with ruling case law on the point in the United States.

The International Court of Justice, on May 28, 1948, gave an advisory-opinion concerning the conditions of admission of a state to membership in the United Nations. By nine votes to six it held:

The field of international law in general is sharply demarked from that of municipal law, but it is the individuals, composing the population of the various states and nations, who furnish the points of contact where international friction may be generated. With the claims of a citizen or subject against his own government, and its officers and agencies, international law naturally has nothing to do. But when an individual asserts a claim against a government not his own, or against the individuals who carry on its operations, such a claim falls on one side or the other of the boundary between international law and municipal law, according to whether the claimant has or has not an adequate remedy in the ordinary courts of the state against which the claim exists.