It seems only natural to begin the study of international law with a description of its sources. After all, whether as practitioner or scholar a person cannot begin to ask or answer questions about international law until he or she has some sense of what the law is. This requires in turn a basic grasp of the processes whereby international legal norms and regimes come to exist. Thus students of international law must engage immediately with some of the most basic questions in the philosophy of law: what is law, and what is a legal order or system.

These questions frame much of Professor Besson's excellent discussion of the sources of international law. In this essay I seek to build upon a number of Besson's arguments regarding the nature of law and legal order, and her use of those arguments to describe and evaluate both existing and possible though currently non-existent sources of international law. Occasionally I argue at length in support of a particular conclusion, but more often I aim simply to indicate avenues for future research and debate. As will become clear, many theoretical questions regarding the sources of international law remain in need of further exploration.

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Copyright © 2010 Oxford University Press. This chapter first appeared in The Philosophy of International Law.

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