"No person shall be deprived of his life or personal liberty save in accordance with law."
Article 9(1) of the Constitution
Basically this means you cannot be arrested without a lawful reason.
If you believe that your detention is unlawful, you can make a complaint and the High Court can look into this. If the judge is not satisfied that the arrest is lawful, the judge can order that you be produced before the Court and set free.
You have to be told as soon as possible, the reasons for your arrest and you can choose a lawyer to represent you. If you are arrested and not released, you have to be brought before a magistrate with 48 hours of your arrest. You can only be detained further if the magistrate says so. However, the rights in this paragraph do not apply to:-
- an enemy alien (that's an enemy of Singapore);
- a person arrested for contempt of Parliament;
- a person arrested and detained in the interest of public safety, peace and good order; and/or
- a person arrested and detained for drug treatment and rehabilitation.