Introduction:
Jammu and Kashmir is the Indian state that has its own separate constitution, distinct from the Constitution of India. This special status was granted to Jammu and Kashmir under Article 370 of the Indian Constitution.

Background:
At the time of India's independence in 1947, Jammu and Kashmir was a princely state ruled by Maharaja Hari Singh. Unlike other princely states that acceded to either India or Pakistan, Jammu and Kashmir wanted to remain independent. However, with the outbreak of violence and the threat of invasion from Pakistan, Maharaja Hari Singh sought assistance from India.

Instrument of Accession:
Under the terms of the Instrument of Accession signed by Maharaja Hari Singh, Jammu and Kashmir agreed to accede to India in matters of defense, external affairs, and communications. However, the state retained its own separate constitution and a degree of autonomy in other matters.

Article 370:
Article 370 of the Indian Constitution was introduced to provide a legal framework for the special status of Jammu and Kashmir. This article granted the state a wide range of powers and autonomy, including the ability to have its own separate constitution.

Provisions of the Jammu and Kashmir Constitution:
The Constitution of Jammu and Kashmir was adopted on 17th November 1956. It defines the powers and responsibilities of the state government, including its legislative, executive, and judicial branches. The constitution also outlines the fundamental rights and duties of the citizens of Jammu and Kashmir.

Special Status:
The special status granted to Jammu and Kashmir under Article 370 allowed the state to have its own separate flag and the power to define its own permanent residents. It also restricted the application of laws enacted by the Indian Parliament to the state, except in matters of defense, foreign affairs, and communications.

Recent changes:
In August 2019, the Indian government revoked the special status of Jammu and Kashmir by abrogating Article 370. The state was reorganized into two separate union territories - Jammu and Kashmir, and Ladakh. As a result, the separate constitution of Jammu and Kashmir ceased to exist, and the state came under the direct control of the central government.

Conclusion:
Jammu and Kashmir is the only Indian state that had its own separate constitution, distinct from the Constitution of India. This special status was granted to the state under Article 370, which was revoked in 2019.