This chapter argues there is a “pull” toward cross-fertilization on procedural questions, meaning cross-fertilization between international courts and tribunals may be more likely for procedural issues than in substantive law. It describes cross-fertilization in relation to procedural issues. Procedural cross-fertilization is a process and is not just about borrowing by adjudicators, but involves contributions by a range of actors. Three considerations facilitate procedural cross-fertilization and even make it somewhat likely: the discretion of adjudicators on procedural issues, adjudicators’ duty to decide numerous procedural issues, and sociological considerations concerning the circulation of a small number of personnel across multiple fora. However, two considerations counterbalance adjudicators’ broad discretion. On one hand, control mechanisms operated by states push adjudicators to remain faithful to their mandates, limiting the space for procedural cross-fertilization. On the other hand, procedural cross-fertilization feeds and is fed by an emerging model of international due process that is affecting all areas of international adjudication.

As has been widely acknowledged and documented, there has been an impressive increase in interstate litigation over the past decade. More than ever, international courts and tribunals are being regularly engaged by a wide array of states, from north and south, seeking peaceful and authoritative resolution of their disputes. These disputes include disparate subject-matters including but not limited to armed conflict, land and maritime border disputes, territorial sovereignty, global trade, human rights, diplomatic relations and consular affairs. This surge of interstate litigation needs to coincide with an increase in academic attention to the field. Questions such as how the courts and tribunals function, who the arbitrators and judges that decide cases are, which rules of independence and impartiality apply to them, and why a certain method of dispute settlement is preferred, have now become more relevant than ever. An ample collection of rules and decisions now exists to permit such comparative studies. Surprisingly however, little attention has so far been given to the procedure before the various courts and tribunals dealing with interstate disputes from a comparative perspective. While important works have been published on the rules and procedure of specific courts and tribunals, notably the ICJ the ITLOS and the WTO DSU, engagement with the rules and procedure applicable in interstate litigation from a comparative perspective has received little attention.