Brunei–Malaysia border which are defined by agreements, from west to east, are as follows: Brunei and Malaysia in an Exchange of Letters on 16 March 2009, agreed to affirm the five agreements. The two countries also agreed to use the watershed principle to determine the remaining undelimited portions of the border. Brunei's maritime boundary with Malaysia until the 100 fathom isobath was inherited from the Sarawak (Definition of Boundaries) Order in Council 1958 No 1518 and the North Borneo (Definition of Boundaries) Order in Council 1958 No 1517, both of which defined the boundary between Brunei on the one hand, and Sarawak
Brunei–Malaysia border Petronas Carigali Sdn Bhd and US-based Murphy Sabah Oil Co. Ltd for two areas, which Malaysia calls Block L and Block M, which lie exactly within the area claimed by Brunei as part of its continental shelf/EEZ. Later in March 2003, a Bruneian gunboat was sent to drive away a Murphy drilling ship in the area. The following month, the Malaysian navy sent several gunboats into the disputed area to block the arrival of a Total ship. After a tense stand-off involving a single patrol craft from Brunei, Total backed off and both sides stopped work in the disputed areas.