Introduction

Indonesia advanced its claim to Pulau Sipadan and Pulau Ligitan based on a number of arguments. The linchpin of its submissions was that it held a legal title over these two islands as a result of historical circumstances; the Anglo-Dutch Boundary Convention of 1891; and the process of ratification of the said Convention which involved proceedings in the Dutch Parliament, especially those pertaining to the Explanatory Memorandum Map of 1891. To Indonesia, possession of a legal title was paramount, and no amount of subsequent effectivités could displace such a title; they could only enhance it. Indonesia built its case on four major bases as stated below:

Indonesia's Case Based on the Possession of a Legal Title

Legal Title Derived From Historical Developments

In its written Memorial, Indonesia went to great lengths to explain the uncertain nature of the traditional territorial boundaries in the northeastern region of Borneo in the nineteenth century. The explanation was necessary as the native rulers paid more attention to control over people rather than territory. As such, territorial concessions made by local rulers to European powers in the region in the nineteenth century often overlapped so much so “that this lack of precision in determining territorial possessions in the area was the source of confusion among the colonial powers themselves”. The Memorial of Indonesia, vol. 1 proceeded to explain that the Sultan of Bulungan had jurisdiction over territories as far as Batu Tinagat, situated at parallel 4°19’ north on the northeast coast of Borneo. The Sultan of Bulungan, Muhammad Khahar-Oedien had signed a Contract of Vassalage with the Netherlands Indies Government on 12 November 1850, by which he acknowledged submission to Dutch overlordship as far back as 1834. Indonesia claimed that Article II of the 1850 Contract of Vassalage contained definitive evidence that the islands of Sipadan and Ligitan belonged to the Sultan of Bulungan.