This book assembles critical contributions on the work of TRS Allan, the Professor Emeritus of Jurisprudence and Public Law at the University of Cambridge, whose leading work in legal and constitutional theory spans almost 45 years. Allan has charted a distinctive path for legal, political, and moral theory and practice and has become a highly significant figure in the UK and in common law/parliamentary systems around the world. His ideas challenge established opinions about constitutional law within these systems as well as established views about the rule of law from more abstract or philosophical perspectives. Allan claims that law and morality find an inherent connection through the rule of law. He argues that there is a connection that flourishes in common law jurisdictions because although Parliament has sovereign legislative powers, its laws gain their full legal meaning only through an interpretive lens. This lens seeks to reconcile sovereign will with legality's basic moral ideals, especially the idea that law must be general and capable of guiding behaviour and thus respectful of the equality and dignity of its subjects. Allan's scholarship is powerful yet controversial, and it has inspired 20 leading scholars from the UK, Canada, Australia and New Zealand to engage with the central themes of his work. By doing so, the contributors help to make that work accessible to a new generation of scholars and students. They also provide a timely framework for engaging in the most important challenges facing our democracies today: how our legal systems do, or do not, honour and respect democracy and therefore legislative sovereignty while at the same time honouring and respecting the rule of law, or the 'Promise of Legality'.