The President may declare a state of emergency only when "the life of the nation is threatened by war, invasion, general insurrection, disorder, natural disaster or other public emergency" and if the ordinary laws and government powers are not sufficient to restore peace and order.
[1] The declaration is made by proclamation in the Government Gazette and may only apply from the time of publication, not retroactively.
It can only continue for 21 days unless the National Assembly grants an extension, which may be for at most three months at a time.
Emergency measures can violate the Bill of Rights, but only to a limited extent.
Emergency measures may not indemnify the government or individuals for illegal actions.