Putin surely deserves that and much worse but such a measure would not be wise. The so-called Westphalian convention of state relations stemming from the settlement of the Thirty Years’ war in Germany confer legitimacy and a large measure of personal immunity on the leaders of diplomatically recognized states. The assassination of foreign government leaders or their targeting as presumptive criminals is considered illegal under international law and an act of war.
Plenty of people wanted GWB tried for war crimes, or Nixon for supposed involvement in the downfall of Allende (who apparently committed suicide) in 1973. JFK knew about the plot against Diem in 1963 but apparently expected him to be exiled rather than executed. Nikita Khrushchev was apparently taken by surprise by the assassination of JFK--he didn't order it. (Castro maybe...but maybe it was the CIA and he probably wasn't a CIA agent.)