The appalling George Galloway (a British Member of Parliament) says that the assassination of Tony Blair would be "morally justified." Christopher Hitchens in Slate has the story.
By the way, I do agree that the assassination of an enemy Prime Minister is, as a matter of the laws of war, quite a different matter than the deliberate targeting of civilians who aren't participating in the war effort. Likewise, a Nazi attempt to assassinate Winston Churchill during World War II would not have been a war crime of the same sort as Nazi deliberate murders of civilians. (Depending on the circumstances, it might not have been a war crime at all, or it might have been a far lesser violation of the law of war.) Similarly, if al Qaeda were to simply attack the Pentagon, that too would not be a war crime on the level of deliberate targeting of civilians, though of course it would amply justify continued military retaliation against those who are making war on us. (I can't speak with similar confidence about the actual 9/11 attack on al Qaeda, because it involved a hijacked civilian aircraft, which might make the analysis different.) Not all of one's enemies' military attacks are at the same time inherently atrocities -- for some, the actions' moral repugnance stems from the ends to which they're aimed, rather than the means that are used -- though the attacks should be dealt with by force even when they aren't atrocities.
My point, therefore, is not that Galloway's position is an endorsement of the most serious sorts of war crimes. Rather, Galloway's position simply shows, as the title of the post indicates, that he's on the side of his country's (and my country's) enemies.