Plus assasins/murderers within a dominion are handled by the laws of the land. What about foreign mercenaries? Will the mastermind of the Indian PM stand trial in India?
Remember that Elam struggle would not have been possible if not for India's support. The LTTE were trained and armed by India. Killing its PM will not be appreciated by its citizens, no matter which side of the aisle they belong. Only rabid anti-nationals and linguistic chauvinists will argue otherwise.