AbstractThis book explores and assesses two essential features in investor state dispute resolution (ISDS): the selection and the removal of arbitrators. Both topics have received increasing scrutiny and criticism, that have in turn generated calls for reforms. In its first part, this book explains the selection of arbitrators procedurally and comparatively under the most-often used arbitration rules. It then reviews critically the necessary and desirable qualities for arbitrators’ selection and appointment, and addresses some important and related policy issues, such diversity and repeat appointments. Finally, it discusses the recent calls to review the methodologies used to appoint arbitrators, and specifically the proposal by the European Commission to create a permanent tribunal to resolve international investment disputes, the UNCITRAL Working Group III Reform Process and the rules amendment proposal undertaken by the Secretariat of the International Center for Settlement of Investment Disputes (ICSID Secretariat). In its second part, the book addresses the companion and similarly important issue of challenging and removing arbitrators. It does so by reviewing first the provisions that are appplied under a variety of arbitration rules to remove arbitrators who fail to possess the necessary qualities to sit in arbitral proceedings. It then evaluates the reasons for challenge and discusses some important cases that addressed challenges. The book assesses appointments and removals in a multifaceted and comprehensive way, and includes a critical assessment of the reasons and calls for reform of the ISDS system.