On Saturday, the United States, in a joint operation with Israel, killed Iran’s supreme leader, Ayatollah Ali Khamenei. For the first time in the postwar era, Washington has succeeded in killing a foreign leader—shattering a precedent that had been sustained for decades by a mix of moral, political, and logistical concerns.Fifty years ago, in February 1976, President Gerald Ford signed Executive Order 11905, which directed that “no employee of the United States Government shall engage in, or conspire to engage in, political assassination.” There should be no tears in the democratic world for Khamenei, who for four decades oversaw a repressive state with terroristic tentacles that extended throughout the world. But it is worth looking at why presidents of both political parties have long been wary of the state-sponsored killing of foreign leaders.As a U.S. representative, Ford was a member of the Warren Commission, which investigated the assassination of President John F. Kennedy. The experience affected him profoundly. During a site visit to the Texas School Book Depository, the members of the committee took a rifle similar to the one used by Lee Harvey Oswald and looked through its scope at the traffic circulating below. “Kennedy had been my friend,” Ford later recalled. “The thought we were reconstructing his assassination sent a chill down my spine.”[Karim Sadjadpour: The death of Khamenei and the end of an era]When Ford learned as president that the CIA had engaged members of the Mafia in a failed effort to kill Fidel Castro during the Dwight Eisenhower and Kennedy years, he was dismayed and quickly decided to form a special commission to investigate abuses by the intelligence community and suggest reforms. Only days after announcing the formation of the Rockefeller Commission in January 1975, Ford accidentally shared at an off-the-record lunch with executives and editors from The New York Times that his concern about abuses involved assassinations. While awkwardly trying to make a point about the continuing importance of secrecy, Ford told his guests that he had learned of some CIA activities that, if made public, would undermine the reputation of his Cold War predecessors. When asked for an example, the president absentmindedly responded, “Like assassinations.” Although the Times respected the ground rules, this was too juicy not to leak.Within a month, the president’s comment became news, and public reaction to it and to earlier reporting about the CIA by the journalist Seymour Hersh sparked two congressional investigations into the assassination plots—the better-known panel was led by Senator Frank Church. Despite his unintentional leak, Ford was already predisposed to doing something to end this dark presidential legacy. “Although none of these assassinations had been carried out,” Ford later wrote in his memoirs, “the fact that government officials had even considered them was distressing.” A year later, Ford signed the executive order to make sure such operations didn’t happen again.Ford’s successors actually broadened the scope of his assassination ban. First Jimmy Carter and then Ronald Reagan dropped the qualifier of “political.” Reagan directed that “no person employed by or acting on behalf of the United States Government shall engage in, or conspire to engage in, assassination.” Reagan’s version of the assassination ban remains in effect, last amended by George W. Bush in 2008. President Trump didn’t revoke it.Ronald Reagan, George H. W. Bush, and Bill Clinton nevertheless wrestled with this self-imposed prohibition. After Libyan secret security blew up a West Berlin disco frequented by American servicemen—instantly killing a Turkish woman and a U.S. Army sergeant—in April 1986, Reagan sought to kill Muammar Qaddafi. The U.S. Air Force, in Operation El Dorado Canyon, targeted his residence but missed him. The administration rationalized that it had targeted Libya’s command and control and that Qaddafi, as head of the Libyan military, wasn’t a political target. When the CIA reported Qaddafi’s new location, Reagan considered a second strike but then dropped the idea.Iraqi President Saddam Hussein’s palaces were targeted by both Bush, in 1991’s Operation Desert Storm, and Clinton, in 1998’s Operation Desert Fox. Bush, who had been Ford’s CIA director, didn’t order Saddam’s elimination but hoped for it. “If Saddam’s military would take matters into their own hands and get rid of this tyrant, we would then have a real chance” of removing Iraq as a threat to allies in the region, he wrote in his diary in February 1991. “Our goal is not the elimination of Saddam Hussein, and yet in many ways it’s the only answer in order to get a new start for Iraq in the family of nations.”Clinton, after receiving hard evidence of an Iraqi attempt to kill Bush during a postwar visit to Kuwait, launched a salvo of 23 tomahawk missiles at six buildings of the Iraqi intelligence headquarters in Baghdad. Seven years later, in December 1998, after Saddam blocked United Nations inspections of his alleged weapon-of-mass-destruction facilities, Clinton included six of the dictator’s palaces as targets of the 650 bomb sorties and 400 cruise missiles in the four-day Operation Desert Fox. Killing Saddam wasn’t Clinton’s main goal—getting the inspectors back in was—but the president wouldn’t have been upset if Saddam had been taken out by an explosion.Clinton had no interest in negotiating with Osama bin Laden, but he worried that the assassination ban posed a legal complication for any plan to kill bin Laden. After al-Qaeda blew up U.S. embassies in Kenya and Tanzania, Clinton ordered a cruise-missile strike against bin Laden’s headquarters in southern Afghanistan, as well as against an alleged al-Qaeda-directed WMD facility in Sudan. A few additional opportunities to kill bin Laden later materialized, but Clinton felt that the intelligence was not firm enough to risk killing innocents, losing military assets, or facing public criticism. As the 9/11 Commission determined, Clinton had authorized lethal action against bin Laden only if he couldn’t be captured, thus complicating the missions and leaving the CIA uncertain as to whether the agency was being directed to kidnap bin Laden or eliminate him. As one CIA manager told the commissioners, “We always talked about how much easier it would have been to kill him.”Ford’s ban had been on political assassinations, and bin Laden wasn’t a head of state. But since the 1970s, presidents had doubted the public appetite for assassination attempts of any kind and been unsure of their legal status. That changed after 9/11. The public became broadly supportive of Washington targeting and killing individual terrorists, Congress gave President George W. Bush a blank check to use all “necessary and appropriate force” against al-Qaeda, and, just as significant, new technology made it possible to pursue the approach. Armed predator drones allowed commanders to surveil and target individuals. In 2011, President Barack Obama used the technology to kill Anwar al-Awlaki, a U.S. citizen living in Yemen. Through it all, the public seemed unfazed by presidents administering these faraway death penalties or even by reports of innocents killed as “collateral damage.”President Trump’s authorization of the assassination of Qassem Soleimani in 2020 indicated how far we had come. As head of the Quds Force of the Islamic Revolutionary Guard Corps, Soleimani was part of a state-directed Iranian terrorist network that had killed, among others, American and allied soldiers in Iraq. The U.S., however, was not actually at war with Iran, which meant that Soleimani was a political target of sorts. Drones and presumably a new level of intelligence capabilities raised the likelihood of success.After October 7, 2023, the Israeli assassination campaign against leaders of Hamas and Hezbollah revealed lethal intelligence capabilities that could only have been dreamed of in the predigital Cold War. In addition, the U.S. was apparently able to blind both Tehran during last year’s raid on Iranian nuclear facilities, and Venezuela this year during the capture of President Nicolàs Maduro and his wife—a fact that indicates the concerns about the loss of U.S. pilots to anti-aircraft systems (which complicated Reagan’s, Bush’s, and Clinton’s efforts to punish, if not kill, foreign leaders) are now much diminished.[Graeme Wood: Why Khamenei is dead]In November 1960, a representative of Eisenhower’s State Department asked at a covert-action-planning meeting whether “any real planning had been done for taking direct positive action against Fidel, Raul [Castro], and Che Guevara,” because “without these three, the Cuban government would be leaderless and probably brainless.” The CIA’s response at that point was that “action of this kind is uncertain of results and highly dangerous in conception and execution.” Because the plan required eliminating all three simultaneously, the agency concluded that the “suggestion is beyond our capabilities.”If tasked with a similar assignment in 2026, the intelligence community and the military would likely have the tools to target any political leader on the face of the planet. This is an enormously consequential shift in the foreign-policy tools available to a president. Killing anyone, let alone a dangerous foreign leader, without a trial involves a moral choice. Killing a foreign leader involves a strategic calculation with questionable odds. A regime isn’t a chicken; decapitating it doesn’t necessarily bring about its death after a short dance. Indeed, in the modern age, no police state has died by assassination alone.As killing foreign leaders gets easier for us, harming our leaders also presumably gets easier for others. The international taboo against foreign political assassination has arguably had a stabilizing effect, despite those states—Russia, for example—that have flouted it. To put a fine point on it, however tempting it may be to eliminate troublesome foreign leaders, no policy maker in a democracy wants to spark acts of retaliation that cost the lives of our own leaders in turn.