The Constitution of Singapore is silent as to the interaction between international law and Singapore domestic law. However, it is accepted in practice that whether there is a treaty in force between Singapore and another State is settled by the executive.
Although the executive does not need Parliament’s consent to enter into treaties, merely entering into treaties does not create rights or duties that can be enforced in Singapore courts. The treaties must be transposed into domestic law by legislation before rights and duties are created. Only Parliament has the power to transpose treaty law into domestic law, even if refusing to do so would amount to a treaty violation.
Similar to the executive and Parliament, the Singapore courts adhere strictly to the principle of separation of powers. Hence, the court cannot assess the desirability of or the wisdom behind the treaties entered into by the executive, and can only review the relevant domestic law where treaties have been incorporated into domestic law by Parliament.. The courts can do so by construing the effect of this legislation or by declaring the statutory provision null and void if it violates the Constitution. In discerning Parliament’s intent behind the domestic legislation, the courts apply the presumption that Parliament intends to adhere to international law and international comity. Section 9A(2) of the Interpretation Act (Cap 1, 2002 Rev Ed) has been construed as being wide enough to encompass international law when giving effect to legislation which was meant to give effect to Singapore’s international law obligations.
Apart from treaty law, the Singapore courts generally adhere to the doctrine that customary international law may be invoked in the Singapore courts as part of the common law. However, the customary international law that is received would still remain subject to the hierarchy of domestic legal sources. In other words, customary international law is received into Singapore as part of the common law and would still be subject to statutes and the Constitution. This remains the case even if the customary international law norm in question is jus cogens (ie, a peremptory norm). Of course, Parliament is free to legislate customary international law norms into statute, at which point it would be construed as all other statutes would, and would take precedence over the common law.
Finally, proof of international law is not usually considered to involve proof of fact, unlike proof of foreign law. However, this is a point that has not been tested in the Singapore courts.
Source:
www.singaporelaw.sg