Acquiescence

A factor in the formation of customary international law and prescriptive

rights whereby consent to a rule is not in the form of positive statements or action, but

takes the form of 'silence or absence of protest in circumstances which … demand a

positive reaction in order to preserve a right': MacGibbon, The Scope of Acquiescence

in International Law, (1954) 31 B.Y.I.L. 143 at 182. See Lotus Case (1927) P.C.I.J., Ser

A, No. 10 ; Anglo-Norwegian Fisheries Case 1951 I.C.J. Rep. 116 at 139. In treaty law,

under art. 20(5) of the Vienna Convention on the Law of Treaties of 23 May 1969 ( 1155

U.N.T.S. 331 ), 'a reservation is considered to have been accepted by a State if it shall have

raised no objection to the reservation by the end of a period of twelve months after it was

notifi ed of the reservation or by the date on which it expressed its consent to be bound

by the treaty, whichever is later'. In relation to acquisitions of territory, acquiescence

refers to the conduct of a State competing for title or the State with former title to the

territory; cf . recognition . See Grisbådarna Arbitration (1909) 11 R.I.A.A. 155 ; Island of

Palmas Case (1928) 2 R.I.A.A. 829 ; Frontier Land Case 1959 I.C.J. Rep. 209 . And see

Bowett, Estoppel before International Tribunals and Its Relation to Acquiescence, (1957)

33 B.Y.I.L. 176 .[1]

Estoppel by Acquiescence

The entry “acquiescence” in the Parry and Grant Encyclopaedic Dictionary of International Law (currently, the Encyclopaedic Dictionary of International Law, 2009), Oxford University Press