Yet it is often considered the exclusive domain of professionals with years of legal training. International law shapes nearly every aspect of our lives. This second edition text uses clear, accessible writing and contemporary examples to explain where international law comes from, how actors decide whether to follow it, and how it is upheld using legal and political tools. Suitable for undergraduate and graduate students, this book is accessible to a wide audience and is written for anyone who wants to understand how global rules shape and transform international politics.