I oppose the death penalty but make an exception for war criminals.
The thing is that there is no universal definition on war criminals, or at the very least that each nation will subjectively target to war criminals to what harm they did to a certain nation or not, while others would be spared simply for allying the winners of a war, or the "right side".
If an exception should be made for war criminals, people like W. Bush for instance should be executed as well, but thats something you hear people not say often.
I am going to vote "no", because the execution of an execution will always be flawed (reasoning), and also forms a threat to diplomats of certain nation. What harms diplomacy, eventually harms all of us.