By tradition, jurists, statesmen, and scholars have looked exclusively to two factors – (1) widespread state practice and (2) manifestations of a conviction that the practice is required by international law – to divine whether an emergent rule has attained customary international law status. This book has examined the largely overlooked role of a third factor – a context of fundamental change – that can serve as an accelerating agent, enabling customary international law to form much more rapidly and with less state practice than is normally the case.

Historically, crystallization of new rules of customary international law was viewed as a protracted process that took decades, if not centuries, to complete. Indeed, the term “crystallization” is often employed by the International Court of Justice and scholars to equate formation of customary rules with the slow growth of crystalline minerals. While working on this book, I was invited to tour the headquarters of the Kyocera Corporation in Kyoto, Japan, which is headed by the patron of Case Western Reserve University’s Inamori Ethics Prize. Among the products Kyocera manufactures are recrystallized gemstones. Just as Kyocera is able to create precious gemstones in a short time under intense heat and pressure, so too can a context of fundamental change intensify and accelerate the formation of customary international law.