Part One of the Constitution of India

Part I—The Union and Its territories is a compilation of laws pertaining to the constitution of India as a country and the union of states that it is made of.

This part of the constitution contains the law in the establishment, renaming, merging or altering the borders of the states or union territories. This part contains four articles. These articles were invoked when West Bengal was renamed, and for formation of relatively new states such as Jharkhand, Chhattisgarh.

says that India shall be a union of states composed of states and union territories (as listed in Schedule 1) and any acquired territories as admitted in article 2. Article 1 mandates a federal structure in which all the citizens of the country shall have at least two tier governance with second tier as locally elected state government unless it is not feasible due to unavoidable limitations. With the seventh amendment to the constitution in 1956, the concept of union territories is brought to administer areas which are very small in area or governed by international agreements or politically not evolved for locally elected governance. Sikkim was admitted as a state in Indian union on 26 April 1975. There is no other area forming part of India excluding its states and union territories. The representation of seats in council of states (Rajya Sabha) shall be given in Schedule 4 of the constitution.The territorial waters and the exclusive economic zones shall also become part of the states or union territories in the absence of any listing of them separately in Schedule 1 and 4 of the constitution. There is no separate representation in parliament though people inhabit on these offshore areas for exploiting resources such as fisheries, oil and gas, etc.

The constitution (40th amendment) act, 1976, was passed during the emergency period and received Presidential assent on 27 May 1976. It substituted a new Article 297 so as to vest in Union of India all lands, minerals, and other things of value underlying the ocean within the territorial waters or continental shelf or exclusive economic zone of India.

...
Wikipedia