Book excerpt: This study examines the reservations to the acceptance of compulsory jurisdiction included in declarations made by States under Article 36(2) of the Statute of the Permanent Court of International Justice and of the Statute of the International Court of Justice and discusses the practical application by the Court of the principle of reciprocity to such reservations in contentious cases submitted to it under Article 36(2). It has been considered that, due to acceptance conditioned by so many, diverse, and complicated reservations, the compulsory jurisdiction of the Court has been declining in significance. The recent trend of acceptance of the compulsory jurisdiction does not support such a conclusion. Since the practice of making declarations with reservations has continued, further study of the Court's jurisprudence in dealing with such reservations seems necessary. This analysis attempts to show that reservations in unilateral declarations do not contribute to the decline of the Optional Clause. In fact, reservations provide for the flexibility which many States consider essential in accepting the compulsory jurisdiction of the International Court of Justice. Thus, the right to include a variety of reservations in unilateral declarations may in fact contribute to the wider acceptance of compulsory jurisdiction.