In 1951 only two of the five permanent members of the UN Security Council (UNSC) were parties to the CPPCG: France and the Republic of China. The CPPCG was ratified by the Soviet Union in 1954, the United Kingdom in 1970, the People's Republic of China in 1983 (having replaced the Taiwan-based Republic of China on the UNSC in 1971), and the United States in 1988. In the 1990s the international law on the crime of genocide began to be enforced.