India is a federation with a parliamentary system governed under the Constitution of India, which serves as the country's supreme legal document. It is a constitutional republic and representative democracy, in which "majority rule is tempered by minority rights protected by law". Federalism in India defines the power distribution between the federal government and the states. The government abides by constitutional checks and balances. The Constitution of India, which came into effect on 26 January 1950, states in its preamble that India is a sovereign, socialist, secular, democratic republic. India's form of government, traditionally described as "quasi-federal" with a strong centre and weak states, has grown increasingly federal since the late 1990s as a result of political, economic, and social changes.
The federal government comprises three branches:
Executive: The President of India is the head of state who is elected indirectly by a national electoral college for a five-year term. The Prime Minister of India is the head of government and exercises most executive power. Appointed by the president, the prime minister is by convention supported by the party or political alliance holding the majority of seats in the lower house of parliament. The executive branch of the Indian government consists of the president, the vice-president, and the Council of Ministers—the cabinet being its executive committee—headed by the prime minister. Any minister holding a portfolio must be a member of one of the houses of parliament. In the Indian parliamentary system, the executive is subordinate to the legislature; the prime minister and his council directly responsible to the lower house of the parliament.
Legislative: The legislature of India is the bicameral parliament. It operates under a Westminster-style parliamentary system and comprises the upper house called the Rajya Sabha ("Council of States") and the lower called the Lok Sabha ("House of the People"). The Rajya Sabha is a permanent body that has 245 members who serve in staggered six-year terms. Most are elected indirectly by the state and territorial legislatures in numbers proportional to their state's share of the national population. All but two of the Lok Sabha's 545 members are directly elected by popular vote; they represent individual constituencies via five-year terms. The remaining two members are nominated by the president from among the Anglo-Indian community, in case the president decides that they are not adequately represented.
Judicial: India has a unitary three-tier judiciary, consisting of the Supreme Court, headed by the Chief Justice of India, 21 High Courts, and a large number of trial courts. The Supreme Court has original jurisdiction over cases involving fundamental rights and over disputes between states and the Centre; it has appellate jurisdiction over the High Courts. It is judicially independent and has the power both to declare the law and to strike down union or state laws which contravene the constitution. The Supreme Court is also the ultimate interpreter of the constitution.