The recent leak of a Justice Department "white paper" purporting to justify the remote-controlled drone killing of an American citizen without charges or trial raised anew the question whether President Obama's counterterrorism policy is more a continuation than a refutation of his predecessor's controversial and much-criticized approach.

Peter Baker wrote in The New York Times that President Obama has "embraced some of Mr. Bush's approach to counterterrorism."

Notre Dame Law School Professor Mary Ellen O'Connell compared Obama's authorization of drone strikes to the Bush administration's secret memos authorizing the CIA to subject terror suspects to waterboarding and other abusive interrogation tactics.

John Yoo, author of the Bush administration's initial "torture memos," got into the act himself, contending in The Wall Street Journal that drone strikes "violate personal liberty far more than the waterboarding of three al Qaida leaders ever did."

But claims that Obama is channeling Bush are grossly exaggerated. While both chose to use military as well as law enforcement measures to respond to the threat posed by al Qaida, there is a world of difference between the approach Bush took to war powers and that taken by President Obama.

Where Bush treated the law as an inconvenient obstacle to be thrust aside in the name of security, Obama has sought to pursue al Qaida within the framework of the laws of war. Many of Obama's policy choices deserve criticism, to be sure. And his reliance on secrecy is particularly disturbing. But to paint the two leaders with the same brush is to miss the difference between a leader who seeks to evade the law, and one who seeks to abide by it.

There are certainly disquieting parallels between the authorization of drone strikes and the authorization of torture. Both relied on secret Justice Department memos that redefined terms in ways that defy common sense.

Where the torture memo said that only pain of the intensity associated with "organ failure or death" constituted torture, the drone memo argues that the United States can kill in self-defense even where no attack is underway or being planned, radically redefining the traditional requirement of an "imminent" attack as only George Orwell could have.

Where the torture memo claimed that "enhanced interrogation" was not barred by a federal law against torture, the drone memo argues that killing an American in Yemen with a drone does not violate a federal statute that prohibits killing an American abroad.

Both memos were secret until leaked to the press. (Indeed, all of the underlying memos authorizing drone strikes remain secret; the white paper is merely an unclassified summary of one such memo.) And both the Bush and Obama administrations have sought to dismiss any legal challenge to their policies by declaring them secret.

But these similarities should not obscure a fundamental difference. Under the laws of war, international human rights and the U.S. Constitution, torture is never lawful.

The Bush administration sought to institutionalize the infliction of cruelty and torture as a tactic in its "war on terror," in the face of overwhelming authority that it is never a permissible option. Killing, by contrast, is an inevitable if regrettable aspect of war. No law, treaty or constitutional provision prohibits killing the enemy in wartime, or in self-defense.

On the contrary, the Constitution recognizes the authority to engage in war, and the laws of war permit the use of lethal force as long as it satisfies basic requirements of targeting only the enemy, minimizing collateral damage and the like. Killing in war time by drone is no more or less legal than killing by bazooka, bayonet, or bomb.

Nor is there anything inherently unconstitutional about killing American citizens. President Lincoln authorized the killing of hundreds of thousands of Confederate soldiers, but no one claims that violated due process.

If an American were fighting with al Qaida on the battlefield against us, few would contend that due process bars our soldiers from shooting back at him. There is no dispute that the taking of an American's life must comport with due process, but there are significant questions about what due process requires in a war setting.

Admittedly, there are many disputes about the applicability of the laws of war to a conflict between a state and a nonstate actor, such as al Qaida, and about the geographic scope of such a conflict where the nonstate actor may operate in a number of different locales, some far from any traditional battlefield.

But the point is that they are difficult and unresolved questions; by contrast, there is no question about the legality of torture.

Thus, where Bush sought to rationalize a universally proscribed war crime, Obama is seeking to chart an appropriate legal course in a new setting of a well-established and generally lawful military tactic: killing the enemy.

Bush's modus operandi was to evade the law -- by keeping detainees beyond our borders where it argued, the law did not reach; by holding some in secret prisons away from the prying eyes of even the International Committee of the Red Cross; by arguing that no judicial review extended to any of them; by treating the Geneva Conventions as "quaint" and inapplicable; and by asserting his power as commander-in-chief to override any law that he deemed inconvenient when "engaging the enemy."

His administration seemed to see law, almost as much as it saw al Qaida, as the enemy.

By contrast, President Obama has insisted since day one that he will fight within the confines of the rule of law. He closed the CIA's secret prisons, forbade "enhanced interrogation," confined interrogation to that permitted by the Geneva Conventions and the Army Field Manual, pursued all domestic terrorism cases through the civilian criminal courts, rejected the notion that the commander-in-chief can ignore laws he does not like, and vowed to close Guantanamo.

He has been unable to follow through on the last promise, but this is largely owing to congressional opposition. In his May 2009 speech on national security, Obama insisted that he would fight terror while remaining true to our values and the rule of law. And he hasn't just said so in speeches.

When a three-judge panel of the Court of Appeals for the D.C. Circuit in 2010 ruled that the international laws of war did not constrain the president's detention powers, President Obama took the virtually unprecedented step of telling the court that it had granted him too much power. He maintained that his detention authority was constrained by international law, and the Court en banc agreed, rendering that part of the panel's decision nonbinding dicta.

Much of the continuing controversy over Obama's counterterrorism policy stems from underlying disagreements about the propriety and scope of the war. If one takes peacetime as a baseline, the use of lethal force and military detention rather than criminal processes to deal with terrorism is entirely unacceptable.

In times of peace, we prosecute terrorists, accord them fair trials, and incarcerate them only upon conviction. In times of war, by contrast, we can detain and kill the enemy's fighters without trial. So if one disputes the propriety of our war against al Qaida, then all the military means Obama has deployed are problematic.

If, by contrast, one concedes that we remain at war with al Qaida - see, for example, the boots on the ground in Afghanistan - then the use of military means, such as killing and detention, ought not to be controversial, so long as they comport with the laws of war. Can anyone really object to the use of a drone, for example, to kill an al Qaida operative on the battlefield in Afghanistan?

A more nuanced - and credible - critique of Obama would acknowledge that for the moment we are at war in Afghanistan, but maintain that the existence of that conflict should not justify the use of lethal force or other military measures thousands of miles away, in Yemen or Somalia, where we are not at war, and where the groups we have targeted did not even exist when al Qaida attacked us on 9/11.

Not all uses of military force beyond a battlefield are impermissible. In World War II, we captured enemy soldiers far from any battlefield, and no one suggested we could not do so. And if a nation faces a truly imminent threat of attack, it may use lethal force as a last resort in self-defense, even if the threat comes from nowhere near an active battlefield. But whether and to what extent lethal force may be used in Yemen or Somalia is deeply controversial, even if one accepts the existence of an ongoing armed conflict with al Qaida.

That controversy is fueled by the unacceptable level of secrecy with which the Obama administration has shrouded its drone program. The leaked white paper gives us the most detail yet on the program, but it still leaves many crucial questions unanswered.

Should the president ever be able to kill American citizens without acknowledging that he has done so, or does due process forbid the killing of one's own citizens in secret? Can deliberate killing of noncitizens go unacknowledged, or does that violate the prohibition on "forced disappearances"?

What procedures and standards of proof are employed to ensure that those targeted for drone strikes are in fact fighting for al Qaida against us? What is the appropriate definition of "associated forces"?

How does the ease of killing with a drone affect the assessment of whether capture is feasible, as capture will always entail more risk to Americans? Is it permissible to treat all al Qaida leaders as presumptively presenting an "imminent" threat justifying lethal force in self-defense, or does that violate the purpose of the imminence requirement, namely to ensure that lethal force is a last resort?

Why shouldn't a court or some other independent entity provide oversight, before and/or after the fact, to ensure that the standards are being adhered to in practice?

These questions will continue to dog the Obama administration as long as it keeps its program largely under wraps. Killing in wartime, unlike torture, is sometimes permissible.

Asserting and exercising the power to use lethal force against enemies in a war should not be confused with asserting and exercising the authority to torture. But drones raise new and difficult questions, because they make it possible to kill far from any battlefield, without putting American lives at risk, and in stealthy and deniable ways.

These questions deserve full and deliberate consideration in a democracy. If President Obama is committed to fighting terror within the rule of law, he needs to be much more transparent about his exercise of this power.

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David Cole is a professor of constitutional law and national security at Georgetown Law, and a fellow at the Open Society Foundation.