The dispute between Hungary and Slovakia concerning the Gabcïkovo-Nagymaros project could easily be described as one of the most important cases to come before the International Court of Justice (“the Court”) in recent years. The case raised a number of very important questions of international law, many of which had received no previous consideration in the Court's jurisprudence. In the first place, the Court was asked by both parties for orders of specific performance. Although the competence of the Court to issue orders of specific performance or injunctive relief had been the subject matter of much discussion in the academic literature, the issue had never before been raised squarely before the Court. Second, this was the first dispute in which the Court was directly asked to consider the consequences of the legal developments in the field of environmental protection. Despite the proliferation of treaty developments in that field, the status of many of those norms remains problematic Third, although the relationship between the law of treaties and the law of State responsibility has generated much general interest, the Court had not in the past been presented with an opportunity to pronounce on some of these issues. Finally, this is also one of the few cases in which the Court has been asked to consider the legal implications of State succession outside the context of decolonisation.