For those who are not familiar with international law, just what it is or how it operates is often a puzzle. Some will doubt whether there even is such a thing, or, as it is often put, whether international law really is law. To answer this question, one must consider the forms that international law takes and how it functions. This analysis begins with a consideration of how law works in general and then proceeds to examine international law to consider how it resembles and how it differs from the law most people—lawyers and non-lawyers alike—are familiar with. Much international law remains customary. Even when a norm of customary international law has been determined with some certainty, the customary form of enforcement—claim and counte...