Originally uploaded in SSRN. Chapter in Interpretation in International Law (Andrea Bianchi, Daniel Peat & Matthew Windsor, eds., Oxford University Press, 2015)


Precedent presents a puzzle for international law. As a matter of doctrine, judicial decisions construing international law are not-in-and-of themselves law. They are not binding on future parties in future cases, even before the same tribunal. And yet, international precedent is everywhere. From international investment to international criminal law to international human rights to international trade, prior decisions are invoked, argued over, and applied as precedents by practitioners and by tribunals.

How and why do certain interpretations of international law take on the weight of precedent, reshaping international law arguments around them, while others do not? This chapter develops a framework for explaining the emergence of precedent in international law that can begin to solve this puzzle. It focuses on three sets of factors relevant to a prior interpretation’s precedential weight, (1) the varied potential sources of precedent, (2) the factors that might imbue a source with authority, (3) and the actors and audiences who might invoke a precedent or respond it, before weaving them into three overlapping accounts of how these factors interact, (1) a rationalist account, (2) a jurisprudential account, (3) and a sociological account. The chapter ends with a couple of case-studies that demonstrate how these factors and accounts can help explain the actual patterns of precedent we observe in international law today.