A U.S. missile attack targeting al-Qaida's second-in-command killed 18 people in a Pakistani village early Friday morning. Pakistan's government lodged a "strong protest" with the American ambassador the next day; public protests followed. This is the fourth such assault in the last few months, and it comes just a few weeks after the Pakistanis formally protested a Jan. 7 helicopter attack that killed eight people. Are these cross-border strikes against the law?
It depends on whom you ask. The attacks raise two legal questions: First, was the decision to launch the airstrikes consistent with international law? Second, did the attacks themselves fulfill accepted standards for military conduct? International-relations scholars categorize these questions as relating to jus ad bellum (the "law to war") or jus in bello (the "law of war").
According to the principles of jus ad bellum, as codified in the U.N. charter, one nation can attack another only in self-defense. That doesn't mean you can launch a full-scale attack in response to a tiny incursion. In 1842, U.S. Secretary of State Daniel Webster laid out a doctrine of legitimate self-defense that scholars and government officials have cited again and again. Webster said you can only attack when the necessity is "instant" and "overwhelming." The jus ad bellum tradition also stipulates that a nation's act of self-defense should be proportional to the threat against it.
Some legal scholars say the missile strikes in Pakistan are clearly against the law since Pakistan never attacked the United States. Others argue that the rules of war need to be updated, since terrorist groups, like states, can engage in major armed conflict. By that logic, the recent attacks on Pakistan are similar to the post-9/11 invasion of Afghanistan; i.e., both were legitimate acts of self-defense against al-Qaida.
This dispute is irrelevant if the Pakistani government gave the United States permission to carry out the missile strikes. If so, that could make the attack legal whether or not the U.S. had a valid claim to self-defense. Few nations in Pakistan's position would admit that they had struck such a deal, so it's possible that the formal diplomatic protests are for show.
What about the way in which the attacks were conducted—the jus in bello question? Is killing 18 people in Pakistan against the law? The traditional rules of war say you can't target civilians, but that civilian deaths are acceptable as long as they are proportional to the overall military objective. (The U.S. military takes care to outline these legal issues in its manuals.) The latest missile strike was designed to kill al-Qaida's second-in-command, which is an important and valid military goal if you accept the jus ad bellum argument above.
Bonus Explainer: Do governments ever pay reparations for an illegal attack? Sometimes, but they rarely admit they were wrong. In 1988, the United States sent the Iranian government about $30 million after the USS Vincennes shot down a commercial airplane with 290 people aboard. In making the payment, U.S. officials denied wrongdoing and called the attack a "justifiable defensive action." (Iraq had paid the United States three times as much per casualty for a wrongful attack on a U.S. naval vessel the year before.)
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Explainer thanks Mark Drumbl of Washington and Lee University and Steven Ratner of the University of Michigan.
Correction, Jan. 18, 2006: The photograph of a man holding a piece of ordnance that originally ran with this story was removed after readers brought our attention to a New York Times correction that pointed out the caption information provided by Agence France-Presse was inaccurate. The unexploded ordnance was not the remains of a missile fired at a house.