After addressing some preliminary points, the presentation first stresses the importance of distinguishing clearly between jurisdiction and applicable law. Then it considers how a court or tribunal whose jurisdiction ratione materiae is largely con fined to the interpretation and application of a particular treaty may nevertheless refer to general international law. The author suggests six possible ways in which recourse may be had to general international law and analyzes the case-law of the International Tribunal for the Law of the Sea in that regard. He then points out the relevance of expertise in general international law for the composition of the Tribunal. By way of conclusion, the author suggests that when any court or tribunal acting under a limited conferral of jurisdiction has recourse to general international law, it should—in the interest of transparency and so as to avoid the appearance of an excess of jurisdiction— explain the basis on which it is doing so. In his view, the Tribunal has made an important contribution to the law of the sea and to certain issues of general international law while acknowledging that the law of the sea can only be properly understood within the context of international law as a whole.