If patriotism is, as Samuel Johnson suggested, the last refuge of a scoundrel, then self-defense is the last refuge of an aggressor. The justification of self-defense comes readily to the lips of both paranoids and those who reasonably wish to defend themselves against imminent attack. The argument for America's putative invasion of Iraq is, of course, self-defense, that is, the need to shield itself and its allies against Saddam Hussein's possible use of weapons of mass destruction.
But claims of "self-defense" also find less reputable invocations. Timothy McVeigh, the Oklahoma City bomber who murdered 168 people in 1995, thought he was defending the US Constitution against a predatory federal government. Yigal Amir thought he was defending Israel against a Prime Minister willing to surrender sacred land to the enemy when he assassinated Yitzak Rabin later in the same year.
Perpetrators of violent acts rarely concede that they are aggression pure and simple, rather than actions in defense of life, liberty, or some other important value. Is there a sensible boundary between sense and nonsense in claiming self-defense? Lawyers must seek this distinction, for if we surrender to the rhetorical claims of statesmen and paranoids, the line between aggression and self-defense will disappear.
The UN has tried to delimit the scope of self-defense, but it goes too far by permitting states to resort to force only if "an armed attack occurs." This makes little sense, because states must retain the right to defend themselves against impending attacks as well.