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.

Thus, the amendments validly operated to deprive the applicant Teo Soh Lung of the ability to apply to the courts for judicial review.

On 21 May 1987, Teo Soh Lung, a lawyer, was detained under the Internal Security Act ("ISA")[1] of Singapore together with other persons for purported involvement in a conspiracy to overthrow the Government by force and replace it with a Marxist state.

[2] Teo's application for a writ of habeas corpus succeeded before the Court of Appeal in Chng Suan Tze v. Minister for Home Affairs ("Chng Suan Tze")[3] as there was insufficient evidence of the President's satisfaction that her detention without trial was necessary to prevent her from acting in a manner prejudicial to the security of Singapore or the maintenance of public order, pursuant to section 8(1) of the ISA.

Notwithstanding the provisions of any other written law, no appeal shall lie to the Judicial Committee of Her Britannic Majesty’s Privy Council in any proceedings instituted by way of judicial review in respect of any decision made or act done under this Act or in respect of any question of interpretation of the provisions of Part XII of the Constitution or any law made thereunder.

Section 8B(1), which stated that the law governing the judicial review of any decision made or act done in pursuance of any power conferred upon the President or the Minister by the Act shall be the same as was applicable and declared in Singapore on 13 July 1971, reaffirmed the law governing judicial review as laid down in the High Court's 1971 decision Lee Mau Seng v. Minister for Home Affairs,[11] which was rendered on that date.

[13] Section 8B(2) provided that there was to be judicial review only in regard to any question relating to compliance with any procedural requirement of the ISA governing such act or decision.

[16] Counsel for Teo argued that the House of Lords decision in Anisminic Ltd. v. Foreign Compensation Commission[17] was applicable on the facts.

At the most, the case decided there was a presumption that an ouster clause did not prevent a court from inquiring whether a public authority had been acting outside its jurisdiction when making an administrative decision.

However, it was clear from the provisions of the ISA that it was for the Executive to determine whether, as a matter of policy and judgment, certain activities were prejudicial to national security.

Since the Minister had stated that the Cabinet and the President acting in accordance with the Cabinet's advice were satisfied that Teo had acted in a manner prejudicial to the security of Singapore by being involved in a Marxist conspiracy to establish a socialist state, allowing the court to investigate into the good faith of the President or the Minister would be inconsistent with the scheme intended by Parliament.

Further, relying on the Indian Supreme Court cases Kesavananda Bharati v. State of Kerala (1973),[19] Minerva Mills Ltd. v. Union of India (1980)[20] and P. Sambamurthy v. State of Andhra Pradesh (1986),[21] Parliament's powers to amend the Constitution were limited by implied limitations derived from the basic structure of the Constitution itself.

The amendments merely reaffirmed the law which the courts had followed since Lee Mau Seng, and ensured that the legislative intent behind the ISA was not disregarded.

The Teo Soh Lung decisions cannot be read apart from Chng Suan Tze and the series of legislative and constitutional amendments made by Parliament.

Chng Suan Tze departed from decades of the court abiding by the policy of non-justiciability, and held that "the notion of a subjective or unfettered discretion is contrary to the rule of law.

[30] Following the amendments to the Constitution and the ISA, the High Court in Teo Soh Lung had the opportunity to reassert the principles set down in Chng Suan Tze.

However, Lee Mau Seng appears to be bad law since it was overruled by the Court of Appeal in Chng Suan Tze.

Furthermore, as a High Court decision, Lee Mau Seng may not be the final word on judicial review of action taken under the ISA.

This is because the statute "does not substitute a new, detailed regime covering all the various issues, such as grounds of review, the rules of natural justice, the meaning of ultra vires, remedies and locus standi".

[33] Teo Soh Lung is also significant because the High Court denied the application of the basic features doctrine in Singapore.

"[34] In Malaysia, the basic features doctrine was also found to be inapplicable by the Federal Court in Phang Chin Hock v. Public Prosecutor.

Such changes may not have happened or may have faced the possibility of being pronounced unconstitutional by the courts if the basic features doctrine was applicable in Singapore.