Singapore became an autonomous state within Malaysia, with its own constitution, on September 16, 1963. It separated from Malaysia on August 9, 1965. On December 22, 1965, the Legislative Assembly passed a Singapore Independence Bill and a Constitutional Amendment. The Constitutional Amendment provided for a parliamentary system of government, with a president, whose duties were largely ceremonial, elected every four years by the Parliament.

The Constitution can be amended by a two-thirds vote of Parliament. A 1966 amendment allowed appeal from the Court of Appeal in Singapore to the Judicial Committee of Her Majesty's Privy Council (see Glossary) in Britain. In 1968 an amendment created the office of vice president and liberalized the requirements of citizenship. A 1969 amendment established the Supreme Court in place of the High Court and Court of Appeal as the highest appeal tribunal. A 1972 amendment entitled "Protection of the Sovereignty of the Republic of Singapore," introduced a measure to ensure the sovereignty of the city-state. It prohibited any merger or incorporation with another sovereign state, unless approved in a national referendum by a two-thirds majority. Under the same terms, it also prohibited the relinquishment of control over Singapore police forces and armed forces. In 1978 the Fundamental Liberties section of the Constitution (Part IV, Articles 9-16) was amended the amendment extended government powers by establishing that arrests to preserve public safety and good order and laws on drug abuse would not be inconsistent with liberties set forth in that section of the Constitution.

Data as of December 1989