evidence: Ashmore and Cartier Islands is an Australian external and federal territory off the northwest coast of Western Australia. [...] A British order-in-council dated 23 July 1931 stated that Ashmore and Cartier Islands would be placed under the authority of the Commonwealth of Australia when Australia passed legislation to accept them, and formal administration began two years later. The Commonwealth's resulting Ashmore and Cartier Islands Acceptance Act 1933 came into operation on 10 May 1934, when the islands formally became a territory. The act authorised the Governor of Western Australia to make ordinances for the territory. In July 1938 the territory was annexed to the Northern Territory, then also administered by the Commonwealth, whose laws, ordinances and regulations applied to the Northern Territory. When self-government was granted to the Northern Territory on 1 July 1978, administration of Ashmore and Cartier Islands was retained by the Commonwealth. [...] Landscape [edit]The territory comprises Ashmore Reef, which includes West, Middle, and East Islands, and two lagoons, and Cartier Reef, which includes Cartier Island. Ashmore Reef covers approximately 583 km2 (225.1 sq mi) and Cartier Reef 167 km2 (64 sq mi), both measurements extending to the limits of the reefs.