The Court found that the Maroua Declaration constituted an international agreement concluded between States in written form and tracing a boundary; it was thus governed by international law and constituted a treaty in the sense of the VCLT (see Art 2, para l), which reflects customary international law in this respect. The Court further considered that it could accept the argument that the agreement was invalid. It observed that while, in international practice, a two-step procedure consisting of signature and ratification is frequently provided for in provisions regarding entry into force of a treaty, there are also cases where a treaty enters into force immediately upon signature. In the Court’s opinion, the Maroua Declaration entered into force immediately upon signature.

The Advisory Opinion of the Court was requested by the UNGA in the following terms: ‘In so far as concerns the Genocide Convention, in the event of a State ratifying or acceding to the Convention subject to a reservation made … can the reserving State be regarded as being a party to the Convention while still maintaining its reservation if the reservation is objected to by one or more of the parties to the Convention but not by others …?’

The Court determined that if a party to the Convention objects to a reservation which it considers to be incompatible with the object and purpose of the Convention, it can in fact consider that the reserving State is not a party to the Convention; if, however, one party accepts the reservation, then the reserving State is considered a party to the Convention.