For most of the past two hundred years or more - the grand era of national constitution-making - founding fathers and constitutional scholars alike seem to have focused more sharply on questions of legislative power than they have on executive power. Executive power, by contrast, they worried much less about and sought to delimit less thoroughly. The scope of executive power and its accountability are however endemic problems, which arise within federal and non-federal states. Nor are these issues unique to common law constitutional orders. Problems concerning the nature and delimitation of executive power also arise in civil law jurisdictions and in the European Union. Despite the historical constitutional focus on legislative power, it is executive authority which seems in the early 21st-century to be the more threatening. This book addresses two sets of questions that are under-researched in constitutional scholarship. What is the proper scope of executive authority, how is executive power delimited, and how should it be defined? How is executive authority best held to account, politically and legally? These questions are both descriptive and normative and they are addressed accordingly in each of the chapters by leading public lawyers from a variety of jurisdictions. The book examines executive power in the United Kingdom from a British and from a distinctively Scottish perspective. There are chapters on the four common law jurisdictions of Australia, New Zealand, Canada, and the United States; on the four civil law jurisdictions of France, Germany, Italy, and Spain; and on the European Union. This insightful comparative perspective allows themes to be drawn together, and lessons extracted on the nature of executive power and its accountability.