This is a pre-copyedited, author-produced version accepted for publication Max Planck Encyclopedia of International Procedural Law following peer review. The version of record is available at https://opil.ouplaw.com/display/10.1093/law-mpeipro/e2442.013.2442/law-mpeipro-e2442?rskey=DlEbp7&result=1&prd=OPIL