ABSTRACT
Acceptance of and objections to reservations to general multilateral treaties raise many complex issues of international law. Traditionally a reservation made subsequent to the conclusion of a treaty required the unanimous acceptance of all other treaty parties, unless the treaty otherwise provided. If any State entitled to object to the reservation did so, either the reservation was withdrawn or the reserving State was not regarded as a party to the treaty. On 18 May 1951 the International Court of Justice rendered its opinion on Reservations to the Convention on the Prevention and Punishment of the Crime of Genocide. Notwithstanding considerable criticism of the majority opinion in the Genocide case, support for the unanimity principle waned. There is no clear consensus in the doctrine as to the legal effect under the Vienna Convention of an impermissible reservation. In practice the flexible system of the Vienna Convention is viewed as working reasonably well.
