Article 370 is a constitutional link between state of Jammu and Kashmir and the Union of India. It was introduced as a temporary provision in the Indian constitution till the state forms its own constitution and decides whether the said article should be amended, abrogated or removed.
Under sub section (3) of Article 370 it was provided that the article can be removed or changed on the recommendations of the constituent assembly. On July 4, 1954, it was decided that the article 370 which was temporary in nature shall remain in force and therefore it became permanent features of the Indian constitution.
It became an un-amendable after the constitutional assembly ceased to exist after 1957.