By definition, international law, once agreed upon and consented to, applies to all parties equally. It is perhaps the one area of law where cross-country comparison seems inappropriate, because all parties are governed by the same rules. However, as this book explains, states sometimes adhere to similar, and at other times, adopt different interpretations of the same international norms and standards. International legal rules are not a monolithic whole, but are the basis for ongoing contestation in which states set forth competing interpretations. International norms are interpreted and redefined by national executives, legislatures, and judiciaries. These varying and evolving interpretations can, in turn, change and impact the international rules themselves. These similarities and differences make for an important, but thus far, largely unexamined object of comparison. This is the premise for this book, and for what the editors call "comparative international law." This book achieves three objectives. The first is to show that international law is not a monolith. The second is to map the cross-country similarities and differences in international legal norms in different fields of international law, as well as their application and interpretation with regards to geographic differences. The third is to make a first and preliminary attempt to explain these differences. It is organized into three broad thematic sections, exploring: conceptual matters, domestic institutions and comparative international law, and comparing approaches across issue-areas. The chapters are authored by contributors who include leading international law and comparative law scholars with diverse backgrounds, experience, and perspectives.