Teo Soh Lung v Minister for Home Affairs is the name of two cases of the Singapore courts, a High Court decision delivered in 1989 and the 1990 judgment in the appeal from that decision to the Court of Appeal. The cases were concerned with the constitutionality of amendments made to the Constitution of the Republic of Singapore and the Internal Security Act ("ISA") in 1989. The latter statute authorizes detention without trial on security grounds. These amendments had the effect of changing the law on judicial review of executive discretion under the ISA by re-establishing the subjective test enunciated in the 1971 High Court decision Lee Mau Seng v Minister for Home Affairs which had been overruled in 1988 by Chng Suan Tze v Minister for Home Affairs, and limiting the right of judicial review to ensuring compliance with procedures specified in the ISA. In other words, the amendments were intended to render the exercise of power by the President and the Minister for Home Affairs under the ISA to detain persons without trial not justiciable by the courts. Both the High Court and Court of Appeal found that these amendments were constitutional because Parliament had done nothing more than enact the rule of law relating to the law applicable to judicial review. Thus, the amendments validly operated to deprive the applicant Teo Soh Lung of the ability to apply to the courts for judicial review.

The Constitution of the Republic of Singapore is the supreme law of Singapore. A written constitution, the text which took effect on 9 August 1965 is derived from the Constitution of the State of Singapore 1963, provisions of the Federal Constitution of Malaysia made applicable to Singapore by the Republic of Singapore Independence Act 1965, and the Republic of Singapore Independence Act itself. The text of the Constitution is one of the legally binding sources of constitutional law in Singapore, the others being judicial interpretations of the Constitution, and certain other statutes. Non-binding sources are influences on constitutional law such as soft law, constitutional conventions, and public international law.