Lawyers usually describe a revolution as a change in a constitutional order not authorized by law. From this perspective, to speak of a ‘lawful’ or an ‘unlawful’ revolution would seem to involve a category mistake. However, since at least the 19th century, courts in many jurisdictions have had to adjudicate claims involving questions about the extent to which what is in fact a revolutionary change can result in the creation of a legally valid regime. In this book, the authors examine some of these judgments.