Why is sanction for prosecution needed?

The story so far: The issue of granting sanction to prosecute a public servant has once again come to the fore, following Karnataka Governor Thawar Chand Gehlot’s approval to open an investigation against Chief Minister Siddaramaiah and to prosecute him in connection with alleged irregularities in the allotment of compensatory plots to his wife whose land had been lost to the acquisition process by the Mysore Urban Development Authority. Section 197 of the Code of Criminal Procedure Code said no court could take cognisance of a case against a public servant unless an authority competent to remove that person grants sanction. We have no doubt in our mind that when there is to be a prosecution of the Chief Minister, the Governor would, while determining whether sanction for such prosecution should be granted or not under s. 6 of the Prevention of Corruption Act, as a matter of propriety, necessarily act in his discretion and not on the advice of the Council of Ministers.” What have courts said on the issue? In Madhya Pradesh Special Police Establishment vs. State of MP and others, the Supreme Court found the Council’s decision “irrational” and upheld the Governor’s action.