services therein". For the purposes of this provision, essential services means services relating to water, electricity, public health, fire, prisons, post, telephony, telegraphy, radiocommunication (including broadcasting and television), ports, docks, harbours, public transport, and the bulk distribution of fuel and lubricants. Instead of detaining a person for the purposes mentioned above, the executive may impose other restrictions upon the person's liberty such as curfews, requiring the reporting of their movements, prohibiting the person from speaking at public meetings or taking part in political activities, and travelling beyond Singapore or any part of the country. Procedure Before detention Before a person can be detained under the ISA, the President must be satisfied that such detention is necessary for the purposes of national security or public order. This is a precondition for the valid exercise by the Minister for Home Affairs of the power to order the detention. The detention order is supplemented by section 74 of the ISA which empowers the police to arrest and detain any person pending enquiries without a warrant under section 8. Initial detention Once an individual has been detained, there are administrative processes which the executive is required to follow under sections 9, 11 and 12 of the Act. The detainee is to be informed of the grounds of detention as soon as possible, unless their disclosure is against the national interest. They are to be served with a copy of the detention order as well as the grounds and allegations of fact on which the detention order was made. The detainee is also to be informed within 14 days of their right to make representations against the order to an advisory board, which is required to hear and consider the detainee's representations. Each advisory board is chaired by a Supreme Court judge appointed by the President, and has two other members appointed by the President in consultation with the Chief Justice. The board has the powers of a court to summon and examine witnesses, and to order that documents be produced. It evaluates the evidence and must make recommendations to the President concerning the matter within three months of the date of detention. When the advisory board recommends the release of the detainee against the Minister's decision, the President exercises personal discretion whether the detainee should be released. Before exercising his discretion, the President is required to consult the Council of Presidential Advisers. Non-citizens detained