This book focuses on the role and content of the principle of the welfare interests of the child, considers the extent to which the principle has changed following its varied elevation by the introduction of paramountcy and reviews the distinction between welfare interests and rights. Providing an updated record of developments in the framework of relevant international law, the book assesses the contemporary relevance of established and emerging themes in the flow of cases dealing with the welfare interests and rights of children in England, Wales, Ireland, the U.S., Canada, Australia, New Zealand, France and Germany. By identifying and analysing the functions of the principle in hybrid proceedings (including adoption from state care and commercial surrogacy) the book completes the analysis of the law relating to children in public (care and protection) and in private (divorce, custody, etc.) family law as a whole, revealing characteristic jurisdictional differences and facilitating a comparative assessment of their significance. By examining the international framework of legislation and related caselaw it identifies and assesses unfolding themes in the law relating to children. In addition to a digest of international cases and legislation that identifies and tracks the role of this principle in civil and criminal law, lawyers, academics and other researchers will find a wealth of information on how it has evolved to reflect corresponding changes in society.