Last week U.N. investigator Philip Alston delivered a report on "targeted killings" in which the U.S. government plays a starring role. Under a policy secretly initiated by George W. Bush and expanded by Obama, the CIA and the Joint Special Operations Command track and kill people, including U.S. citizens, based on their alleged ties to Al Qaeda or its allies. The killings, typically carried out by missiles fired from drone aircraft, dangerously blur the line between warfare and summary execution.

As Alston noted, targeted killings "are permitted in armed conflict situations when used against combatants…or civilians who directly engage in combat-like activities." But "they are increasingly being used far from any battle zone"—in places such as Yemen, where the U.S. fires missiles at "high-value targets" such as the American-born radical cleric Anwar al-Awlaki.

Harold Koh, the State Department's legal adviser, says such attacks are justified by international law and by the Authorization for the Use of Military Force that Congress passed after the September 11 attacks. "The United States is in an armed conflict with Al Qaeda, as well as the Taliban and associated forces," Koh says. "Individuals who are part of such an armed group are belligerents and, therefore, lawful targets."

But unlike a conventional war, this "armed conflict" is fought on a "battlefield" that spans the globe by "belligerents" who do not wear uniforms and are not readily identified. Hence Koh's reasonable-sounding law-of-war argument amounts to claiming that the executive branch has the unreviewable authority to kill enemies that it unilaterally identifies anywhere in the world.

The geographic reach of this license to kill exceeds even that of an old-fashioned tyrant accustomed to shouting, "Off with his head!" Imagine how the U.S. would react if a foreign government claimed it had the right to kill people on the streets of New York because it considered them "belligerents."

Given the breathtaking scope of the authority claimed by the president, the reassurances of his underlings ring hollow. "Whether a particular individual will be targeted in a particular location," says Koh, "will depend upon considerations specific to each case, including those related to the imminence of the threat, the sovereignty of the other states involved, and the willingness and ability of those states to suppress the threat the target poses." This is a long way of saying "trust us."

Last February, Dennis Blair, then the director of national intelligence, assured members of Congress that "we don't target people for free speech." Rather, "we target them for taking action that threatens Americans or has resulted in it."

Awlaki, for example, is known mainly for his inflammatory yet constitutionally protected sermons. But according to an unidentified "American official" quoted by The New York Times in April, "The danger Awlaki poses to this country is no longer confined to words. He's gotten involved in plots."

Before you take the government's word that Awlaki has been marked for death based on something more than his anti-American tirades, consider its track record in justifying the detention of alleged "belligerents." Even though the burden of proof is much lighter than it would be in a criminal trial, the American Civil Liberties Union notes, "the government has failed to prove the lawfulness of imprisoning individual Guantanamo detainees in 34 of the 48 cases that have been reviewed by the federal courts thus far."

Luckily for the government, it does not need to present any evidence against Awlaki or other "high-value targets," because it does not want to detain them. It only wants to kill them.

Jacob Sullum is a senior editor at Reason and a nationally syndicated columnist.

© Copyright 2010 by Creators Syndicate Inc.