Traditionally, highest courts have had the task of safeguarding the unity of law within the territory of their jurisdiction. Their position at the top of the hierarchy of domestic courts meant there was no other authority above them. Globalisation, however, has resulted in changes to the position and function of the highest courts on the national level. The internationalisation of law has brought the individual domestic legal systems into close contact with one another. An invaluable tool for national judges, judges and staff of international courts, civil servants at ministries of justice, this study of the dividing line between the national and international level identifies the contemporary function of the highest national courts.