The post war Japanese immigration policy can be divided into four periods. The first period is during 1952 to 1981, which is characterized by strict immigration regulation. After the legislation of Immigration Control Act (ICA) in 1952 Koreans and Taiwanese lost their Japanese nationality. It was a part of the post war cleanup process. The second period is during 1982 to 1989. After ratifying the ICESCR in 1979 and the Refugee Convention in 1981 the rights of non-nationals were improved. The third period is during 1990 to 2008. The revision of ICA in 1990 opened door for unskilled foreign labor force. The fourth period is from 2009 up to the present. Since the revision of Immigration Control Act in 2009 Japan heads toward strategic recruitment of foreign workers. This paper examines the legal fundaments of the post war Japanese immigration policy especially from the view point of restricted sovereignty.