Jammu and Kashmir is the only Indian state which has its own constitution.
The constitution of Jammu and Kashmir, which was adopted on 17 November 1956 and came into effect on 26 January 1957, is a legal document which establishes the framework of government at state level (in the state of Jammu and Kashmir). The constitution has 158 articles divided into 13 parts and 7 schedules. As of 2002, 29 amendments have been introduced in the constitution.
In 1947, British India was partitioned into India and Pakistan. The princely states were given a choice to join either India or Pakistan or stay independent. At that time, the state of Jammu and Kashmir was ruled by Maharaja Hari Singh who initially chose to be independent and not join any of the two countries. But, Pakistan attacked Kashmir by sending Tribesmen. Because of this attack, Maharaja Hari Singh agreed to joined India by signing the Instrument of Accession with some conditions (which is why Kashmir is a part of India but enjoys a special status).
Under Part XXI of the Constitution of India, which deals with “Temporary, Transitional and Special provisions”, Article 370 was introduced after the independence which provides the state of Jammu and Kashmir this special status to have its own constitution. Article 370 was framed after an extreme negotiation of five months between Jawaharlal Nehru and J&K Prime Minister Sheikh Mohammad Abdullah.
According to Article 370, Parliament of India and the Union Government’s jurisdiction extends over limited matters with respect to the State of Jammu and Kashmir. The actions in all matters, which are not specifically vested in Federal governments, have to be supported by the state legislature. In Jammu and Kashmir, residual powers are also vested in the state government. It is because of these reasons that this state enjoys autonomy unlike other Indian states. Till 1965, the other notable difference between Jammu and Kashmir and other Indian states was that the head of the state in Jammu and Kashmir was called Sadar-e-Rasyat, while in other states the head was called Governor.