A. Introduction

The rise of Islam in Southeast Asia revolutionized specific social institutions in the region. Islam as a politico-religious institution had triggered the modification and introduction of social institutions that shaped present day Southeast Asia. Among the most important developments was the introduction of the sultanate (a developed political and at the same time religion institution) to the region. For the purpose of this research, my study will focused on the development of the Sulu sultanate as part of the greater Malayan world and the eventual claim of the Philippines to Sabah (as the political successor at sovereignty of the Sulu Sultanate).
The objective of this study is to trace the historical and legal basis of the Philippine claim over the State of Sabah. The methodology of the study will be thematical not chronological. Instead of being conscious of the timeline, the study will concentrate on the major themes that shaped the sultanate’s Sabah dominion, lease and agreements with western world and the present claim of the Philippines to the Sabah State. The words “North Borneo,” “British Borneo” or “Sabah” are used interchangeably in the study. These words are used to that portion of the North Borneo Island to which the sultan of Sulu once ruled.
Available historical records seem to indicate that the dispute territory was a possession of the Sultan of Sulu which evidently was leased to the founders of a British chartered company. With protection of the crown guaranteed over the lease territory, later became the foundation British annexation and colonization. Eventually, Sabah was included in the federation of Malaysia.