The Basic Law of the HKSAR was enacted by the National People's Congress in accordance with Article 31 of the Constitution of the People's Republic of China. It is the constitutional document of the HKSAR. It was promulgated on 4 April 1990 and took effect on 1 July 1997 on the establishment of the HKSAR. The systems and policies practised in the HKSAR must be based on the provisions of the Basic Law. These include the social and economic systems; the system for safeguarding the fundamental rights and freedoms of its residents; the executive, legislative and judicial systems; and the relevant policies. Furthermore, no law enacted by the legislature of the HKSAR may contravene the Basic Law.
The most prominent feature of the Basic Law is the underlying principle of "one country, two systems" whereby the socialist system and policies shall not be practised in the HKSAR, and the previous capitalist system and way of life is to remain unchanged for 50 years.
Under the Basic Law, the laws previously in force in Hong Kong (that is, the common law, rules of equity, ordinances, subordinate legislation and customary law) shall be maintained, except for any that contravene the Basic Law and subject to any amendment by the HKSAR legislature. National laws of the People's Republic of China shall not be applied in the HKSAR except for a number of such laws relating to defence and foreign affairs as well as other matters outside the limits of the autonomy of the Region under the Basic Law which are listed in Annex III to the Basic Law.
The National People's Congress through the Basic Law authorises the HKSAR to exercise a high degree of autonomy directly under the Central People's Government. The HKSAR enjoys executive, legislative and independent judicial power, including that of final adjudication, in accordance with provisions of the Basic Law. Although foreign affairs relating to the HKSAR are the responsibility of the Central People's Government, the HKSAR is authorised to conduct relevant external affairs on its own in accordance with the Basic Law. The Central People's Government is also responsible for the defence of the HKSAR, but the responsibility of maintaining public order in the HKSAR is a matter for its government.
The Basic Law details the fundamental rights, freedoms and duties of the residents of the HKSAR. These rights include the right to equality before the law; freedom of speech, of the press and of publication; freedom of association, of assembly, of procession and of demonstration; and the right and freedom to form and join trade unions, and to strike; freedom of movement; freedom of conscience; and freedom of religious belief. The Basic Law also guarantees that the provisions of the International Covenant on Civil and Political Rights; the International Covenant on Economic, Social and Cultural Rights; and the international labour conventions as applied to Hong Kong shall remain in force.
The Chief Executive is the head of the HKSAR and is accountable to the Central People's Government and the HKSAR. He or she is assisted in policy making by the Executive Council of the HKSAR. The Chief Executive presides over the Executive Council and appoints its members.
The main powers and functions of the Government of the HKSAR (which is headed by the Chief Executive) include the formulation and implementation of policies, the conduct of administrative affairs and the drawing up and introduction of budgets and bills.
The HKSAR's legislature is the Legislative Council, and the Basic Law prescribes the specific method for forming the Legislative Council and its procedures for voting on bills and motions. Under the Basic Law, the Legislative Council's functions include the making of laws, approving budgets and public expenditure and monitoring the work of the government in general.