"Drones are a tool, not a policy,” the journalist Jeremy Scahill has written. “The policy is assassination.” All sorts of people use flying robots for all sorts of reasons—Amazon.com has proposed using them to deliver (presumably nonlethal) packages. But five years ago, the U.S. government used the iconic technology of this new century to hunt down and kill one of its own citizens.

That citizen was a New Mexico–born Muslim preacher-turned-terrorist named Anwar al-Awlaki. His killing raises myriad questions, but two are central: How, when, and why did Awlaki, a supposed moderate who spoke out against the 9/11 attacks and was touted by the Bush administration and the media as a voice of reason, become a terrorist dedicated to murdering his fellow Americans? And how did Barack Obama, who ran for president in part on his opposition to Bush-era overreaches in the War on Terror, come to believe he should order the death of a U.S. citizen without charge or trial?

In Objective Troy, Scott Shane tries to answer these questions with a gripping, deeply reported tale of sex, religion, radicalization, and betrayal. In the telling, he reveals a strange truth: the key to understanding Awlaki’s actions, and his fate, is recognizing how American his story is.

Unlike the president who would order his death, Awlaki owed his citizenship to an accident of birth. Both men had secular fathers of Muslim descent and foreign extraction. But Obama’s mother was American, and he would have been American, too, no matter where he was born. Awlaki became a citizen because his Yemeni mother happened to usher him into the world while his father, a scientist from a prominent Yemeni family whom Shane calls a “classic technocrat,” was studying at New Mexico State University. From his first breaths, Awlaki’s future was entwined with that of his nation: without the birthright citizenship guaranteed by the Constitution, it’s hard to imagine he would have been able to build a life in the United States—or acquire the skills that would later make him such a valuable promoter of terrorism. Awlaki spent his teenage years in Yemen but grew up secular. His father, hopeful that Anwar would benefit not only from an American passport but also an American education, sent him back to the states in 1984 to study engineering at Colorado State. It was there that his son got religion.

Shane managed to track down some of Awlaki’s classmates. The stories they tell are of a man who was in many ways a typical young American struggling to find himself as an undergraduate. During winter break his freshman year, Awlaki met some devout Muslims and liked what they had to say. That January, the United States launched Operation Desert Storm against Saddam Hussein’s Iraq, and images of American bombs falling on Muslim cities were on television screens worldwide. A few months later, Awlaki, who suddenly disapproved of Western entertainments, smashed the television of a less-observant Muslim roommate—an act Shane, a reporter for the New York Times, identifies as being driven by the “callow certainty of a recent convert.” Nasser al-Awlaki, Anwar’s father, was more blunt. “What happened,” he tells Shane, “happened in America.”

Shane suggests that Awlaki sought “solace in the clarity of religion when faced with the disorienting temptations and excesses of an American campus”—namely sex, which, as Shane notes, “would become a dangerous trap for Awlaki.” This line is a preview—spoiler alert—of the central revelation of Shane’s book. Why, Shane asks, did Awlaki, who after college became one of the most prominent “moderate” Muslim preachers in the United States, decide to leave a promising post at one of the nation’s largest mosques, flee the country, and turn openly to terrorism? “Like many an evangelical Christian pastor,” Shane concludes, “Awlaki preached against vice and sin, lauded marriage and family, and parsed the Scripture.” But, citing FBI sources and documents he obtained through the Freedom of Information Act, Shane shows that Awlaki didn’t practice what he preached. In the months after 9/11, Awlaki was featured in national media as a “moderate” voice that repeatedly condemned the attacks. He said all the right things. But the FBI, concerned if not paranoid about Muslims, began keeping a closer eye on the preacher. Several of the hijackers had worshipped at mosques where Awlaki worked—a fact that, according to both Shane and the FBI, didn’t necessarily mean much. But the increased FBI scrutiny revealed that Awlaki was regularly visiting prostitutes.

Top FBI officials knew about Awlaki’s activities, and soon a careless agent revealed the bureau’s interest to a motel owner, who told the cleric that the feds knew his secrets. Awlaki was not a secret radical during his time in the United States, Shane argues. Nor did he know of the 9/11 attacks in advance. Rather, Awlaki’s decision to leave the United States for Britain in late 2001 was provoked almost entirely by his worries about the FBI’s probe of his sex life. To what extent Awlaki’s resentment over the FBI’s surveillance led to his eventual radicalization is unclear.

While living in Britain, Awlaki’s rhetoric grew fiercer. In the midst of an angrier, more socially isolated Muslim minority, his “duties and circle of contacts dramatically narrowed,” Shane writes. The cleric became convinced that British intelligence was watching him closely and could snatch him up at any minute and deliver him to the Americans. He was probably right. But “despite his increasingly outspoken criticism of the West and vocal hostility to non-Muslims, he was dispirited by the corruption and inefficiency in Yemen and really would have preferred to settle in America or the United Kingdom,” Shane writes, citing Awlaki’s family. So before he moved to Yemen for good, Awlaki reached out to the FBI, denying any connection to 9/11. No one at the FBI followed up on this overture.

By 2004, Awlaki had settled in Yemen, where he watched the American occupation of Iraq with increasing rage and the United States and local authorities continued to keep an eye on him. But “the more pressure he got from the authorities, the more radical he became,” Awlaki’s brother, Ammar al-Awlaki, told Shane. At one point, the Yemeni government locked him up for a year and a half—and told his family that the Americans wanted him kept in prison. Prison, of course, is where many young Muslims are radicalized. After his release, Awlaki fled to the countryside, where he eventually launched a website and an English-language magazine, Inspire, encouraging would-be terrorists. After Christmas Day, 2009, when a teenager with a bomb in his underwear tried to blow up an airliner headed to Detroit—allegedly at Awlaki’s direction—the former “moderate” became one of the world’s most wanted terrorists. Americanness was Awlaki’s biggest asset. Most Yemeni jihadis were concerned with fights closer to home. But Awlaki could talk to young Western radicals, and urge them to attack places he and they knew well. And he knew exactly how to use Inspire to manipulate the American media.

AS AWLAKI goes into hiding in the Yemeni countryside, Shane brings Obama back to center stage, detailing, as best he can, the president’s decision to order the death of an American citizen. These sections of the book, while not as comprehensive as Shane’s treatment of Awlaki, are nevertheless remarkable, especially given the obstacles posed by the Obama administration’s aggressive prosecution of officials suspected of leaking information to journalists and the secrecy with which its targeted-killing program is conducted.

As Shane notes, the United States has a long history of slaughtering civilians from the skies. From the outset of Obama’s presidency, civilians were dying in air strikes in Yemen. But specifically targeting an American for death—as Obama did when he placed Awlaki on a government “kill list” after the underwear bomber attack—still required some sort of legal justification. Shane ably describes the internal administration discussions—debate is too strong a word—over how that might be concocted. If Awlaki had been Yemeni, no new legal advice would have been necessary, but because he was an American citizen the president had to lawyer up. Obama soon got the permission he wanted.

In November 2010, a U.S. District Court in Washington, D.C., heard a case brought by Nasser al-Awlaki, Anwar’s father, claiming that the president’s decision to place his son on a “kill list” violated Anwar’s Fourth and Fifth Amendment rights. “If the Fourth and Fifth Amendments mean anything at all,” the ACLU’s Jameel Jaffer argued, “surely they mean there are limits to the circumstances in which the government can use lethal force against one of its own citizens.” The judge dismissed the case the following month. Less than a year later, an American drone strike blew Awlaki to pieces.

Awlaki has continued to influence America. As Shane reports, he’s now seen as a martyr, and terrorists, including those associated with ISIS, continue to cite him as an influence, raising the question of whether it would have been more effective to try to capture him—or shame him by releasing evidence of his “extraclerical activities.” So why did Obama, who had condemned the excesses of Bush’s war on terror, embrace targeted killing? The president and his aides, Shane argues, were “radicalized” by events. After the foiled Detroit underwear attack, he reports, Obama urged aides “to imagine the bomb had in fact exploded and the airliner had been destroyed, dwarfing every act of terrorism in the country since 9/11…. Obama would have faced huge political pressure to retaliate.... Obama’s big ambitions on health coverage, immigration, and inequality would have been put aside, probably forever. He might easily have ended as a one-term president.”

As Shane implies but never says outright, the calculus that underlies assassinations of terrorists like Awlaki is inherently political. It would be naïve to expect politicians not to try everything in their power to prevent disasters such as 9/11 or the recent Paris atrocities, even if doing so means violating citizens’ rights. When faced with a choice between security and liberty, most elected officials, like many Americans, choose security.

The U.S. Constitution’s system of checks and balances is supposed to protect individual liberties even in times of national emergency. Yet Congress hasn’t thoroughly investigated the executive branch’s assassination policies, and judges have repeatedly shot down lawsuits over targeted killing. Congress is content to criticize the executive branch’s conduct of military affairs, but does not want the responsibility of authorizing assassinations or declaring war. The courts are reluctant to step into the middle of a dispute between the two branches of government that are given war-making powers by the Constitution.

THE EVIDENCE that Awlaki was actively plotting to kill Americans was, as Shane reveals in the book, overwhelming. But it was also secret. There was no role for the courts, let alone the public—or a jury of his peers—in determining Awlaki’s fate. The congressional intelligence committees are briefed on these operations after they occur, but the decision is the president’s, and the president’s alone.

Shane argues that Awlaki presented an “irresolvable moral quandary.” Citing the “dirty hands” problem often confronted by those charged with protecting the public, Shane concedes that sometimes “the least evil choice available in the circumstances…still leaves an indelible moral stain on the character of the person making the choice.” Awlaki’s killing, he says, fits this model. “Allowing him to operate freely would arguably put at risk the lives of hundreds or thousands of people in a future attack...but killing him without a trial could violate some of the country’s most cherished principles.”

I’m glad I’m not in the position of making these sorts of life-or-death decisions, but I don’t think we can let our leaders off the hook so easily. In contexts other than terrorism—gun control, to cite an example near and dear to the current president’s heart—we’re constantly battling over how to balance American lives against our constitutional freedoms. Jeremy Scahill is right: drones are a tool, not a policy. And it’s the policy we should debate.

The Awlaki strike was about as “clean” as you could wish a drone strike, or any state-directed violence, to be: it killed its target and three other prominent al-Qaeda members without harming any civilians. But not every assassination is so antiseptic. Drone strikes often kill civilians and radicalize survivors. Two weeks after Awlaki’s death, another American drone strike was targeted at an Egyptian al-Qaeda leader. He wasn’t there. The strike killed seven people, including Abdulrahman al-Awlaki, Anwar’s sixteen-year-old son, who was an American. Shane argues, convincingly, that Abdulrahman, a secular teen who liked Harry Potter, decided to join al-Qaeda only after his government killed his father. The Obama administration has never publicly discussed or apologized for that strike. Predictably, the Awlaki family’s efforts to win a reckoning in court went nowhere. The reason we know as much as we do about the killing—and other drone strikes—is because of the efforts of reporters like Scott Shane. Read his book.