President Obama, did or did you not kill Anwar al-Awlaki? There are plenty of problems with President Obama's targeted killings in the war against terrorism: The policy remains secret in most aspects, involves no judicial review, has resulted in the deaths of innocent civilians, has been employed far from any battlefield and has sparked deep anti-American resentment in countries where we can ill afford it. But when it comes to the particular legal issue raised in a recently leaked "white paper" from the Justice Department - namely, whether it is legal to kill Americans with drones - one problem looms largest: The policy permits the government to kill its citizens in secret while refusing to acknowledge, even after the fact, that it has done so. There may be extraordinary occasions when killing a citizen is permissible, but it should never be acceptable for the government to refuse to acknowledge the act. How can we be free if our government has the power to kill us in secret? And how can sovereign authority be accountable to the people if the sovereign can refuse to own up to its actions? When Argentina's military junta secretly abducted and killed its citizens during that country's "dirty war" in the 1970s, the world labeled these acts "disappearances" and condemned them as violations of human rights. A disappearance is not just an abduction or killing, but an unacknowledged abduction or killing. To "disappear" citizens not only deprives them of their liberty or life without fair process but is deeply corrosive of democratic politics, casting a shadow of fear over all. The late senator Daniel Patrick Moynihan once said that if he had to choose between a country with the right to vote but no habeas corpus, or a country that had habeas corpus but no right to vote, he'd choose the country with habeas corpus every time. His point was that if the government has the power to lock up its citizens without having to justify its actions to a court (as habeas corpus requires), all other rights are meaningless. If that's true of detention without judicial review, it is even more true with respect to unacknowledged executive killing. We may think we are free to say what we want, exercise our religion and enjoy the protections of privacy, but none of those guarantees really exists if the president can order us killed in secret. Killing is not like torture. Torture is never justified, even in wartime. But killing is an integral, if unfortunate, aspect of war. Targeted killing is therefore not inherently illegal; after all, it beats the tragically untargeted killing used in the World War II bombings of Dresden, London and Hiroshima. Nor is it always forbidden to kill an American. If a U.S. citizen were fighting alongside al-Qaeda on an Afghan battlefield, would anyone question the right of U.S. troops to shoot and kill him? And President Abraham Lincoln violated no constitutional guarantee by authorizing Union troops to fire on American citizens fighting for the Confederacy. The government can also legally kill Americans in some non-wartime circumstances. The Supreme Court has held, for example, that the Fourth Amendment permits a police officer to use deadly force against a fleeing felon if the felon poses "a significant threat of death or serious physical injury to the officer or others." The FBI team that on Monday killed an Alabama man who had held a 5-year-old boy hostage for nearly a week certainly did not act unconstitutionally.