Sweden v. Yamaguchi, otherwise known as in the matter of Marianne Wilson, or in the matter of Mary Ann Vaughn, is a highly complex decision in international family law which touches on questions in law still unresolved over fifty years later. The formal name of the action was Israel Karl-Gustav Eugene Lagerfelt v. Yamaguchi Masakatsu and Yamaguchi Hideko, or Case of Demand for Delivery of an Infant, No. Wa-154, 1956 Yokohama District Court (Yokohama Chiho-saiban-sho), initiated February 22, 1956. On December 5, 1956, it held that the defendants should deliver the infant to the plaintiff. The appeal was dismissed by Tokyo High Court (No. Ne-2824) on July 9, 1958. Case The case was brought by Consul Baron Karl-Gustav Lagerfelt on behalf of the King of Sweden as petitioner for guardianship of Mary Ann Vaughn, the daughter of a Swedish national in Japan, against the Yamaguchi family, de facto custodians of the eight-year-old child, to answer the questions of custody, guardianship and citizenship of Mary Ann Vaughn, also known as Marianne Wilson. The case was decided in Yokohama District Court in 1956, and sustained upon appeal by defendants to the Tokyo High Court in 1958. Defendants declined appeal to the Japanese Supreme Court, and custody was granted to the Swedish Crown. Mary Ann Vaughn, to be thenceforth known as Marianne Wilson, was granted Swedish citizenship and remained in the custody of the Swedish Ambassadors to Japan Tage Grönfall and later Frederick Almquist in Tokyo. Parental history Mary Ann Vaughn was born the only child of James A. Vaughn (b. May 7, 1925) and Vivienne Joy Wilson (b. November 2, 1929), in Bluff Hospital in Yokohama, Japan on April 17, 1949. Her father was a US national employed under contract with the United States Military Administration of Occupied Japan. Her mother was a Swedish National, of three generations of Swedish citizens resident in Japan. She was descended from John Wilson (Captain) and Sophia Wilson, née Naka Yamazaki (great-grandparents) through their youngest son Professor John Wilson (grandfather). Birth Due to the sensitive nature of Vaughn's employment, the US Military Administration declined to allow Vaughn to marry under civil law at the US Embassy in Tokyo. Vaughn and Vivienne Wilson were married under religious ceremony in Yokohama, Japan on 8 May 1948. The Department of State declined Vaughn's request to allow his wife to immigrate to the United States, due to the absence of