The U.S. has relied on targeted killings in the war against terror. But Qasem Soleimani’s death has sparked debate about whether it was legal.

WASHINGTONWhen a Senate investigation revealed the CIAs plans to execute Cuban dictator Fidel Castro and other leaders, President Gerald Ford moved to ban political assassinations.
Nearly a half-century later, Republican and Democratic administrations have taken advantage of controversial exceptions to Ford’s 1976 executive order. Those exceptions give presidents extraordinary authority to exercise lethal force abroad, testing the limits of international law.
Yet the preemptive strategy now known as targeted killing has never found more currency than in the wake of the 9/11 attacks. Presidents George W. Bush, Barack Obama and now Donald Trump have killed leaders of terrorist groups in order to guard against assaults on the homeland and to protect U.S. interests abroad.
But not even the 2011 killing of Osama bin Laden, the head of al-Qaeda and the architect of the 9/11 attacks, unleashed the barrage of legal questions and global angst that has followed the deadly drone strike against Qasem Soleimani, the once-feared leader of Irans elite Quds Force.
As Iran launched more than a dozen missiles against two military bases in Iraq housing U.S. forces Tuesday night, the act that ignited this confrontation remains the subject of fierce legal debate: Was Soleimanis killing an illegal assassination or a legitimate act in America’s long war on terrorism?
‘An act of war’:Lawmakers react to Iran’s missile strike on US military bases
How we got here:What you need to know about the conflict between the U.S. and Iran after Soleimani killing
The Trump administration has defended the strike as an act of self-defense, claiming Soleimani was engaged in a continuing campaign of terror that placed U.S. interests at “imminent” risk at the moment he was killed in Baghdad.
Nearly a week after the operation, however, national security analysts are at odds, with some asserting Soleimani’s death represented a break with international law that threatens a broad conflagration in the Middle East. 
“The United States had no justification to carry out this strike,” said University of Notre Dame law professor Mary Ellen O’Connell, who specializes in international law and the use of force.
The strike was especially problematic, O’Connell said, because it was launched without the consent of the Iraqi government.
“We don’t have any right to attack on Iraqi soil,” she said.
Indiana University professor David Bosco said international law does provide for countries to act in self-defense from a future attack, provided the threat is imminent.
“If an attack is about to happen, you have authority to hit back, but it’s got to be really urgent,” Bosco said. “We don’t yet know what evidence of imminence had been gathered, but whatever it is, I don’t think it’s going to persuade Iran.”
Soleimani dead:Trump defends Soleimani killing in formal notice to Congress, warns Iran against retaliation
Iran in uproar:Stampede at Iranian commander Qasem Soleimani’s funeral kills at least 56
Pompeo points to attacks leading up to Soleimani killing
On Tuesday, Secretary of State Mike Pompeo appeared to downplay earlier assertions that urgent threats justified the strike on Soleimani. Instead he focused on the Iranian general’s history of attacks on Americans.
“There’s been much made about this question of intelligence and imminence,” Pompeo told reporters. “You need to look no further than the days that led up to the strike that was taken against us,” he said, referring to a rocket attack by Iranian-backed militias on an Iraqi base in Kirkuk on Dec. 27 that killed an American contractor.
That attack led to the assault on the American embassy in Baghdad.
How imminent? Pompeo sidesteps questions about threat posed by Irans Soleimani
But Pompeo has also maintained that the Soleimani operation was properly vetted by legal authorities, saying such a review was standard for “activity of this nature.”
Trump’s national security adviser, Robert O’Brien, defended the decision to kill Soleimani at a White House briefing on Tuesday, though he declined to specify the intelligence that gave officials reason to believe Soleimani was plotting an attack against American forces.
“It was strong evidence and strong intelligence, and unfortunately we’re not going to be able to get into sources and methods at this time, but I can tell you it … was very strong,” O’Brien said.
Trump, too, made no apologies for taking the action.
“We had tremendous information,” the president said Tuesday, declining to elaborate. “Right now, that’s classified. … We saved a lot of lives.”
U.S. law gives broad authority for such strikes
John Bellinger, a former adviser to the State Department and the National Security Council, said Trump had ample authority under domestic law. He cited the president’s broad constitutional authority as commander-in-chief to take action in defense of American interests.
Trump’s national security adviser has said Congress’ 2002 authorization for war in Iraq provided justification for the strike, but Bellinger said that’s an “exceptional legal stretch.” Relying on an 18-year-old authorization for military force, he said, could be “very politically provocative.”
Bellinger said international law may pose the biggest concern. That became more murky Tuesday, he said, when Pompeo appeared to walk back the urgency previously ascribed to Soleimani’s threat.
“There was clear authority under domestic law,” Bellinger said. “The debate is about international law, and the questions about that  based on the administration’s own statements  seem to mount day by day.”
While international law does allow countries to act in self-defense to counter an anticipated attack, Bellinger said the threat must be imminent. In other words, it’s about to happen, not something that could occur soon.
“Secretary Pompeo seems to walk that back,” Bellinger said. “If the threat posed is not imminent, it is not lawful under international law. … One thing we don’t know yet, is what information (the administration) is relying on.”
On Wednesday, administration officials are scheduled to brief lawmakers behind closed doors on their justification for taking an action that has the Middle East boiling over. 
“Now, it is up to Congress to press the president to disclose his legal basis for this action and the plan for how our nation manages the fallout,” said Sen. Chris Murphy, D-Conn. “I doubt there is congressional authority for this strike, and I doubt the president has a plan for what comes next. But these are questions Congress must now ask.”
Contributing: Deidre Shesgreen, David Jackson and Nicholas Wu