If one were to go by Article 156 of the Constitution then the Manmohan Singh government was well within itsrights to sack the governors of Goa, Gujarat, Haryana and Uttar Pradesh. The legal position is that a governorcan "hold office during the pleasure of the President."
But the controversial easing out of governors and replacing them with new appointees has more to do withpolitics than anything else. The UDA government's explanation as articulated by minister of state for home,Prakash Jaiswal, was that the four governors had to be given the marching orders since they were too alignedto the RSS and could not be expected to discharge their functions in an objective manner. At least, onegovernor, Vishnu Kant Shastri, of Uttar Pradesh, proclaimed that he was proud to be a member of the RSS,proving that there was some truth in what both Jaiswal and the Congress party were alleging.