The Notion of an Illegal Occupation in the ICJ’s Palestine Advisory Opinion

Abstract In its Advisory Opinion on the Legal Consequences arising from the Policies and Practices of Israel in the Occupied Palestinian Territory, including East Jerusalem , the International Court of Justice (ICJ) ruled not only that Israeli policies and practices in the occupied territory systematically violated international law, but also that Israel’s ‘continued presence’ (i.e. occupation) as such had become illegal, so that Israel was required to withdraw from the Occupied Palestinian Territories as rapidly as possible. The ICJ’s finding that Israel engaged in a sustained abuse of its position as an occupying power, through annexation of territory and frustration of Palestinian self-determination, was central to its reasoning, as was its holding that the legality of the occupation was to be judged against the jus ad bellum. This article unpacks the concept of an illegal occupation. It argues that, as matter of the jus ad bellum , it is only the right to self-defence that could, in theory, justify Israel’s continued occupation. Curiously, however, the Opinion does not mention self-defence, although it preoccupied many of the judges writing separately. The article argues that two approaches to the occupation’s ad bellum illegality are most persuasive: first, that the occupation could not meet the necessity and proportionality criteria of lawful self-defence; and, second, that even a valid self-defence claim can be vitiated by a predominant ulterior purpose.