But acquiescence can operate as a preclusion or estoppel in certain cases, for instance where silence, on an occasion where there was a duty or need to speak or act, implies agreement, or a waiver of rights, and can be regarded as a representation to that effect

The principle of preclusion is the nearest equivalent in the field of international law to the common law rule of estoppel, though perhaps not applied under such strict limiting conditions (and it is certainly applied as a rule of substance and not merely as one of evidence or procedure).