Even after its accession to the Indian Dominion, J&K's internal administration was governed, not by a diktat of New Delhi, but by the Jammu and Kashmir Constitution Act, 1939. It was under this Act that Maharaja Hari Singh appointed his former adversary, Sheikh Abdullah, as the emergency administrator for the state. The appointment was a victory for the people who simply loved Abdullah. He began giving them a large share in the administration of the state's affairs.
... On May 1, 1951, Yuvraj Karan Singh issued a proclamation declaring the convening of a State Constituent Assembly, consisting of representatives of the people on the basis of adult franchise, for framing a Constitution for the state of Jammu and Kashmir. For the purpose of elections to the proposed Constituent Assembly, the state was to be divided into territorial constituencies each with a population of 40,000 or thereabouts.
Elections to the Constituent Assembly were completed by August that year with the idolised Abdullah's National Conference Party simply sweeping the polls. Addressing its first meeting held on October 31 that year, Sheikh Abdullah declared that the assembly's objectives and functions included, inter alia, a reasoned conclusion regarding accession and the future of the state. He enumerated three alternatives: accession to India, accession to Pakistan and complete independence.
The 'Drafting Committee' of the above assembly presented its report on February 12, 1954. Its report, adopted on February 15, 1954, embodied the ratification of the state's accession to India, with 64 of the assembly's strength of 75 voting unanimously while 11 members were absent.
The State Constituent Assembly enacted, on November 17, 1956, a Constitution that is, today, the Constitution of Jammu & Kashmir. It has 158 Sections. Section 3 therein says, 'The State of Jammu and Kashmir is and shall be an integral part of the Union of India.' Section 147 in it prohibits any bill to amend Section 3 from being introduced or moved in either House of the State Legislature.
Varnam, points to the Aravind Lavakare's article at Rediff on Jammu and Kashmir's accession to India: