A unitary system is governed constitutionally as one single unit, with one constitutionally created legislature. A unitary state is a sovereign state governed as one single unit in which the central government is supreme and any administrative divisions (sub national units) exercise only powers that the central government chooses to delegate.
This is one of the federal features of the Indian constitution.
Art 155 and 156 provide that the Governor, who is the constitutional head of a State, is to be appointed by the President and stays only until the pleasure of the President The Centre may take over the administration of the State on the recommendations of the Governor or otherwise.
It can declare a law as unconstitutional, if it contravenes any provision of the Constitution.
In spite of the fact that the Indian Constitution establishes a federal structure, it is indeed very difficult to put the Indian Constitution in the category of a true federation.
In a federal set up there is a two tier of Government with well assigned powers and functions.
In this system the central government and the governments of the units act within a well defined sphere, co-ordinate and at the same time act independently. Wheare defines federal government as an association of states, which has been formed for certain common purposes, but in which the member states retain a large measure of their original independence.