This post was originally published by The Philadelphia Inquirer. On Wednesday, Hina Shamsi will take part in an Intelligence Squared debate on the question "Does the president have constitutional authority under the due process clause to kill U.S. citizens abroad, or is it a violation of this clause to unilaterally decide to target and kill Americans?"

The White House is once again weighing whether to kill an American citizen overseas as part of its "targeted killing" program.

This extrajudicial killing program should make every American queasy. Based on largely secret legal standards and entirely secret evidence, our government has killed thousands of people. At least several hundred were killed far from any battlefield. Four of the dead are Americans. Astonishingly, President Obama's Justice Department has said the courts have no role in deciding whether the killing of U.S. citizens far from any battlefield is lawful.

The president, it seems, can be judge, jury, and executioner.

This is not the law. Our Constitution and international law strictly limit extrajudicial killing, for good reason. In areas of actual armed conflict, killing can be lawful because of battlefield requirements. Outside that context, an extrajudicial killing is legal only as a last resort, and only in response to a truly imminent threat. This makes sense: If a threat is imminent, there is no time for judicial review. In every other context, the Constitution requires the government to prove its case to a court before it kills. After all, allegations aren't evidence - the difference between the two is due process.

The program's defenders, however, argue that the president must be able to take lethal action against targets "who pose a continuing and imminent threat" and who are too risky to capture, as the president explained last May. But if, as reported, the Justice Department has the time to build a case against a suspected terrorist for months, then the threat he presents is not imminent. And if the threat is not imminent, then the administration's arguments for killing, and against external judicial review, fall away.

The Obama administration has apparently "solved" this logical inconsistency by redefining imminence to mean its opposite. Under the concept of "continuing imminence," the White House says it can order the killing of an American it suspects may someday strike - even without evidence of an actual plot.

The killing program isn't only unlawful, it's unwise.

When Americans hear of a drone strike, many think of a terrorist threat neutralized. But human-rights investigators and reporters have documented numerous horrific casualties of people killed due to mistaken identity or being at the wrong place at the wrong time.

Deaths like these have made the killing program toxic throughout most of the world and have turned potential allies into enemies. The blowback is so severe that retired Army Gen. Stanley McChrystal, who commanded U.S. and coalition forces in Afghanistan, has repeatedly called for restraint. "[T]here is a perception of helpless people in an area being shot at like thunderbolts from the sky by an entity that is acting as though they have omniscience and omnipotence," McChrystal said recently.

Perception isn't the only problem. We would do well to remember the 67-year-old grandmother killed by a drone while picking vegetables in her garden in Pakistan. Or the 16-year-old American boy blown up while eating dinner outdoors in Yemen. Or the 10-year-old Yemeni child who died in a CIA strike - only a few weeks after the president announced that drone missiles would not be fired unless there was a "near certainty" that no civilians would be killed.

There are some powers people should never concede to their government. That's why the Founders included due process in our Bill of Rights. Extraordinary powers consolidated in one office inevitably will be abused. That's true no matter who's behind the desk.

By asserting the right to kill based on his authority alone, President Obama violates the constitutional principles he swore to uphold and undermines the security we all seek. He also paves the way for a President Christie, Clinton, or Cruz to decide who lives and who dies.

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