This article examines the Annulment Mechanism of arbitral awards rendered under the auspices of the International Centre for Settlement of Investment Disputes (ICSID). The primary feature in the ICSID and non-ICSID arbitration regarding the review of awards involves the unified nature of the ICSID system, as compared to the scattered and multi-layered system of review existing under arbitration rules, national legislation, and international convention. This unity can be perceived at different levels. The ICSID annulment mechanism entails only a set of rules; thus, only one set of application standards of review will be implemented, as opposed to sometimes conflicting layers of application rules, laws, and convention, as in the case of non-ICSID arbitration. However, some of the recent annulment decisions have raised serious questions about the breadth of annulment in practice, as opposed to its original design. Nonetheless, implementing a new system under the ICSID awards to be reviewed by an appellate court appears to create more problems than it solves. The potential impact of introducing that mechanism could result in a longer and more complex proceeding, with uncertain benefits.