Only states can be parties in cases before the court. Hence, proceedings may not be instituted by or against an individual, corporation, or other entity that is not a state under international law. However, if certain rules are satisfied, a state may take up a case involving one of its nationals. Thus, the Nottebohm Case (Liechtenstein v. Guatemala), in which a judgment was rendered on 6 April 1955, involved a claim by Liechtenstein in regard to injuries sustained by a German-born, naturalized citizen of Liechtenstein as a result of certain measures that Guatemala had taken during World War II.
All countries that are parties to the statute have automatic access to the court and can refer any case they wish to the court. In addition, the Security Council may recommend that a legal dispute be referred to the court.
Under the Charter, nations are not automatically obliged to submit their legal disputes for judgment. At the San Francisco Conference, it was argued by some that the court should be given compulsory jurisdiction and that UN members should bind themselves to accept the court's right to consider legal disputes between them. This proposal would have meant that if one member filed a case against another member, the court would automatically, and without reference to the second member concerned, have the right to try the case. The proposal was rejected because some delegates feared that such a provision might make the statute unacceptable to their countries. Moreover, it was generally felt that since the disputants in an international court are sovereign states, they should not be summoned against their will to submit to the court's jurisdiction. Thus, the court cannot proceed to adjudicate a case unless all parties to the dispute have consented that it should do so. Such consent comes about mainly in one of the following three ways.
Such declarations may be made for only a limited period if desired and with or without any conditions, or they may state that they will become operative only when a particular country or number of countries accept the same obligation. The most farreaching reservation that has been attached to a declaration is the condition that the court must not adjudicate any dispute that the country itself determines to be an essentially domestic matter. In effect, this reservation leaves the country free to deny the court's jurisdiction in most cases in which it might become involved. In general, the practical significance of many of the declarations is severely limited by the right to make conditions. As of November 2002, declarations recognizing the compulsory jurisdiction of the court had been made by 64 states, with a number of them excluding certain categories of dispute.
The jurisdiction of the court therefore comprises all legal disputes which the parties to the statute refer to it and all matters specifically provided for in the UN Charter or in treaties and conventions in force. In the event of a dispute as to whether the court has jurisdiction, the statute provides that the matter shall be decided by the court. Article 38 of the statute requires that in deciding the disputes submitted to it, the court shall apply the following: (1) international conventions establishing rules recognized by the contesting states; (2) international custom as evidence of a general practice accepted as law; (3) the general principles of law recognized by civilized nations; and (4) judicial decisions and teachings of the most highly qualified publicists of the various nations as a subsidiary means for determining the rules of law. In certain cases, however, if the parties concerned agree, the court may decide a case ex aequo et bono— that is, by a judgment in equity taken simply on the basis of what the court considers is right and good.