This book traces the impact that the International Court of Justice (ICJ), the principal judicial organ of the United Nations, has had on various areas of international law. A number of prominent international experts examine whether, and to what extent, international law has been shaped by the Court's jurisprudence. The informal development of international law through the Court's judgments contrasts with the development of international law through more deliberate means, such as treaty-making. Assessing key areas of international law over which the ICJ has exercised its jurisdiction, such as international environmental law, international human rights, the law of the sea, and the law of immunities, this book comprehensively details the impact of international jurisprudence on contemporary international law. Continuing the work started by Sir Hersch Lauterpacht's influential book The Development of International Law by the Permanent Court of International Justice, this book provides key new insights into the role of the Court in wider international law. It makes required reading for anyone studying the ways in which international courts have in shaped the evolution of international law.