On December 27, 2019, an attack against American interests in Kirkuk, Iraq, wounded several U.S. service members and killed an American citizen. Two days later, in response, the United States conducted targeted air strikes against territories in Iraq and Syria controlled by Kata’ib Hezbollah, an Iraqi militia group with close ties to Iran. Among the targets was Iranian general Qassem Soleimani. Soleimani, leader of Iran’s Quds Force, is believed to be the mastermind behind attacks against U.S. service members, diplomats, and its embassy in Baghdad. The air strikes killed Soleimani and approximately two dozen members of his entourage.

Soleimani’s death has raised questions over its legality. Specifically, some argue President Trump lacked the constitutional authority to authorize the air strikes. Others argue the air strikes were carried out in violation of international law. But under any legal framework, there are legitimate legal bases to justify President Trump’s actions.

Some have claimed President Trump exceeded his constitutional authority because he did not seek congressional approval prior to launching the December 29 air strikes. Yet there is no constitutional requirement that the President obtain congressional authorization prior to taking any military action. The Declaration of War Clause only requires congressional authorization prior to a planned military operation that would constitute a “war.”

The War Powers Resolution of 1973 was intended to curb the president’s unilateral authority to deploy U.S. military forces. The Resolution requires the president to notify congress within 48 hours of committing U.S. military forces to armed conflict. But it does not proscribe the president’s authority, under Article II of the Constitution, to use military force in self-defense. Thus, a president may direct the limited use of military force without congressional authorization. Indeed, the Obama Administration employed this very rationale to support U.S. military actions in Libya.

Those critical of the December 29 air strikes could theoretically claim President Trump lacked any statutory basis to act. But technically, the United States is still operating in Iraq under a 2001 and a subsequent 2002 Authorization for the Use of Military Force (AUMF).

The 2001 AUMF, passed in response to the terrorist attacks of September 11, 2001, authorized the use of American military force “in order to prevent any future acts of international terrorism against the United States by  . . . nations, organizations, or persons.”

The 2002 AUMF paved the way for Operation Iraqi Freedom by authorizing military actions “in order to defend the national security of the United States against the continuing threat posed by Iraq.”

One could argue that Soleimani’s killing is entirely consistent with both AUMFs because he was planning imminent future acts of terrorism against the United States.

Others still have argued that the December 29 air strikes violated international law. Article 2(4) of the United Nations Charter generally prohibits the threat or the use of force by one state against another, but with two notable exceptions: 1) when the use of force is carried out with the consent of the host state; and 2) when the use of force is carried out in self-defense in response to an armed attack, or the imminent threat thereof, and the host state is unwilling or unable to prevent the armed attack.

Iraq did not consent to the use of air strikes to kill Soleimani, so Article 2(4)’s first exception is inapplicable. Thus, the international law question turns on whether the air strikes were necessary as a self-defense measure, and whether the Iraqi government was unwilling or unable to prevent further imminent attacks.

For years tensions between the U.S. and Iran have led to escalating attacks against U.S. personnel and interests in the region for which Iran or its proxies were considered responsible. Secretary of State Pompeo warned that further attacks would be met with a “decisive response.” Yet the Iraqi government—whose prime minister Adel Abdul-Mahdi resigned just one month prior—was unable to prevent the December 27 attack in Kirkuk. And intelligence reports indicated future attacks against U.S. interests were “imminent.”

Under these circumstances, the December 29 air strikes seem to fit neatly within Article 2(4)’s second exception. The U.S. could reasonably argue that it sought to act in self-defense because it had reliable intelligence that Iran was about to carry out yet another armed attack. And despite the fact that Soleimani, an Iranian, was on Iraqi soil, the argument can be made that Iraq was either unwilling or unable to prevent Soleimani’s actions.   

In conclusion, although some might argue against the underlying policy rationale for the December 29 air strikes that killed Qassem Soleimani, there nevertheless are sound legal bases to support the air strikes. Under the U.S. Constitution, domestic, and international law, the president has the authority to use military force to protect the United States, its personnel, and its interests. Congressional authorization is not always required, and although host nation consent is always advisable, there may be circumstances under which it is not a prerequisite. Such is the case with the December 29 air strikes against Soleimani.