We are all familiar with the constant invocations of kastom (the local term in bislama for « custom ») in the political and social life of Vanuatu. The island of Tanna is unanimously considered by all Ni-Vanuatu as the island where kastom seems to be the most respected and the most solid. The people of Tanna are fond of pointing out that, although their island looks no bigger than a match head in world-wide vision, their kastom derives powerful powers from their land, and gives them a strength that they can wield far beyond their shores. We will attempt to clarify the rules of custom in the area of land tenure, and, in addition, we will ask which social agents, individual collecti e or institutional, use invocations of kastom in their attempt to normalise land tenure.