January 2nd marked the second anniversary of the United States’ killing of Iranian General Qassem Soleimani as well as Abu Mahdi al-Muhandis, the deputy chairman of Iraq’s Popular Mobilization Committee, by an airstrike outside the Baghdad airport. That military operation had many long-term consequences. One of the most dangerous is a set of extreme legal opinions drafted during the Trump administration to justify the president’s actions that now lie ready to be used by future presidents.

The Soleimani attack, killing senior military officials of two countries, sparked a dramatic escalation in tensions between the United States and Iran to the highest point  in decades and raised alarm about the safety of U.S. forces throughout the region. Within days, Iran counterattacked with a fusillade of ballistic missiles against US forces at al Assad air base in Iraq. Despite then President Trump’s tweet that “All is well,” the missile attack resulted in traumatic brain injuries for over 100 US troops. Although Trump downplayed their injuries as “headaches,” the Pentagon belatedly awarded dozens of U.S. servicemembers with Purple Hearts.

Worse would follow. After the attack on al Assad, Iran fearing U.S. retaliation, mistakenly shot down a Ukrainian airliner, killing all 176 passengers and crew. This catastrophic mass killing of civilians echoed a similar tragedy when a U.S. warship mistakenly shot down an Iranian civilian airliner in 1988 during the Tanker War, killing 290.

The strike on Soleimani was one of the most perilous moments in U.S. foreign relations under President Trump. Had Iran’s retaliatory missiles killed U.S. service members at Al Assad, the United States, Iran, and the region faced the prospect of a wider war. That the attack on Al Assad did not, in fact, kill U.S. service members was largely a function of chance. Secretary of State Mike Pompeo latter told reporters that that there was “no doubt” that Iran had the “full intention” of killing U.S. personnel.

Even though the United States and Iran avoided a broader conflagration in the short term, we should not be too relieved. The strike on Soleimani had lasting effects on regional security and U.S.-Iranian relations, mostly for the worse. In terms of the use of force, the deeply flawed, yet precedential legal opinions concocted by the Trump administration to justify the reckless operation are a particularly hazardous legacy. The many and manifest shortcomings of the Trump administration’s legal justification have been ably exposed, including by Tess Bridgeman, Ryan Goodman, Oona Hathaway, Adil Haque, Harold Koh, and Steve Pomper, and I will not retread that ground.

Instead, I want to draw attention to the risk these flawed legal justifications pose for enabling future conflicts. As it stands,  the Trump administration opinions and interpretations remain on the books, to be relied upon by the executive branch to justify other unilateral uses of force by the president. These opinions erode the limited internal executive branch constraints on the use of force both under domestic and international law. To mitigate these risks, the Biden administration should disavow and withdraw them.

Legal Background: Executive Branch War Powers Doctrine and the Use of Precedent

Under the executive branch view, the president’s unilateral authority to direct U.S. military forces arises from Article II of the Constitution, which makes the president the “Commander in Chief of the Army and Navy of the United States” and vests in the president the Executive Power.

Relying upon its own prior opinions as precedents, the Justice Department’s Office of Legal Counsel (OLC) has concluded that whether a potential use of military force is within the scope of the president’s unilateral authority under Article II of the Constitution (i.e., his or her power to act without congressional authorization) turns on two questions:

(1) Whether the U.S. military operations would serve sufficiently important national interests; and

(2) Whether the military operations that the president anticipates ordering would be sufficiently extensive in “nature, scope, and duration” to constitute a “war” within the meaning of Article I, § 8, cl. 11, which gives the Congress the power “[t]o declare War.”

As concerns the “national interest” test, first and foremost amongst these is defense of the United States, but over time OLC has identified others as well – from support of the United Nations to mitigating humanitarian disasters. In practice, as Jack Goldsmith, the former head of OLC has noted, the “national interest” test has been applied so broadly by DOJ that it is essentially meaningless as a constraint on executive power. Therefore, to the extent that executive branch war powers doctrine constrains the unilateral use of force by the president under domestic law, it is the second element regarding “war in the constitutional sense” that involves potential limits.

In evaluating whether a proposed military action would amount to such a “war,” and thus require congressional authorization, OLC has looked to the anticipated “nature, scope, and duration” of the operation. Under this framework, military operations will likely rise to the level of war if they are anticipated to be characterized by “prolonged and substantial military engagements, typically involving exposure of U.S. military personnel to significant risk over a substantial period.”

OLC has identified one particularly salient factor in reviewing whether an anticipated military operation amounts to this level of “war in the constitutional sense”: the risk of escalation. In assessing the risk of escalation, OLC has considered whether U.S. forces would suffer or inflict substantial casualties and thus has looked closely at the presence of ground troops given “the difficulties of disengaging ground forces from situations of conflict, and the attendant risk that hostilities will escalate.” In analyzing the proposed deployment of U.S. forces to Bosnia in 1995, for example, OLC noted that due to the presence of U.S. ground forces in a conflict, “Congress may be confronted with circumstances in which the exercise of its power to declare war is effectively foreclosed.”

OLC began to routinely cite “war in the constitutional sense” as a constraint on executive branch war powers during the Clinton administration. Although this test did not feature prominently in the OLC opinions of the George W. Bush administration, it is now ingrained in the bipartisan OLC doctrine. For example, the Trump administration employed this framework in deeming that the United States’ 2018 airstrikes against the Syrian government in retaliation for the use of chemical weapons did not require congressional authorization.

Although this test does not itself appear in the constitution nor has it been evaluated by the courts, it is nonetheless consequential in terms of how the executive branch conceives of its own powers and whether certain military options are discarded as unconstitutional before reaching the president. In policing these boundaries, executive branch lawyers look to past practice as legally meaningful precedent in assessing what national interests justify the use of military force as well as what military operations would amount to war in the constitutional sense. OLC has explained that “two centuries of practice” constitute a “historical gloss” on the constitutional separation of war powers between Congress and the President. As described in Justice Felix Frankfurter’s concurrence in Youngstown Sheet & Tube Co. v. Sawyer, reliance on such gloss as an interpretative approach accounts for the significance of “[d]eeply embedded traditional ways of conducting government [which] cannot supplant the Constitution or legislation, but [that] give meaning to the words of a text or supply them.”

In a somewhat similar fashion as a matter of international law, the executive branch has looked at the past practice of states in gauging the metes and bounds of the “inherent right of self-defense” preserved in Article 51 of the UN Charter. For example, Brian Egan, then Legal Adviser to the State Department, explained in 2016 that “for at least the past two hundred years, States have invoked the right of self-defense to justify taking action on the territory of another State against non-State actors. As but one example, the oft-cited Caroline incident [of 1837] involved the use of force by the United Kingdom in self-defense against a non-State actor located in the United States.”

Precedent for Non-Precedent

Yet the United States does not always treat its own past war powers practice as legal precedent. And the executive branch does so when it knows that certain legal justifications are wrong or dangerous. The modes for avoiding or undoing bad legal positions include: never providing a legal justification for a course of action, formally revoking a past legal justification, and sub rosa abandoning a past legal opinion.

First, the executive branch has previously declined to justify the lawfulness of certain U.S. military operations precisely because it did not wish to create such a precedent. Perhaps the most salient example dates back to NATO’s 1999 Kosovo intervention that the U.S. led despite lacking UN authorization or another valid international law justification. Although the Clinton administration’s OLC defended the U.S. bombing campaign in Kosovo as a matter of domestic law, the administration famously did not claim that the military operation was lawful under international law. Michael Matheson, then Acting Legal Adviser at the Department of State, explained that the United States eschewed legal justifications, including self-defense, out of a desire not to “weaken international legal constraints on the use of force.” He later conceded the United States “mumbled something about [the Kosovo intervention] being justifiable and legitimate,” but this mumbled explanation “was something less than a definitive legal rationale.”

Likewise, though the Trump administration’s OLC issued an opinion justifying his constitutional authority to launch missile strikes against Syria in retaliation for the use of chemical weapons, that administration never sought to publicly justify either the 2018 or 2017 U.S. strikes against Syria as being consistent with international law. (The Trump administration never explained this silence, though John Bolton’s memoir reveals that some officials regarded international law as irrelevant to the strikes.)

Second, the executive branch sometimes goes so far as to unwind a precedent it has already set by affirmatively repudiating specific actions and withdrawing the legal opinions justifying them. In the realm of national security law, both the George W. Bush and Obama administrations withdrew a number of OLC opinions undergirding the U.S. torture program under the Bush administration. President Obama, publicly eschewed the euphemism of “enhanced interrogation” and forthrightly conceded that “we tortured some folks,” an admission that the United States had acted unlawfully.

Third, the executive branch has at times also quietly abandoned prior legal positions without explicitly renouncing them. For example, in 2011 the Obama administration continued military operations against the Government of Libya beyond the 60-day cutoff for “hostilities” under the War Powers Resolution. By way of justification, the Obama administration articulated a novel definition of “hostilities” premised upon a number of factors. But when the Trump administration later explained why U.S. support to Saudi Arabia’s air campaign in Yemen did not constitute “hostilities,” it did not rely on these factors, but instead reverted to an earlier definition of hostilities used by the executive branch since the Ford administration.

Yet, even if unused, expansive precedents and legal theories that are not formally rescinded remain potentially dangerous. So long as these positions are not disavowed and stay on the books, they remain loaded weapons to be used by future executive branch officials. Formal disavowal is necessary to sufficiently reduce this risk.

The Soleimani Legal Opinions

The Trump administration’s legal justifications for the attack on Soleimani are particularly good candidates for rescission.

In the immediate aftermath of the attack on Soleimani, Trump administration officials gave a variety of shifting justifications for the strike (see Karen Greenberg’s excellent summary). The administration’s inability to get its story straight and failure to provide substantiating facts led Senator Chris Van Hollen (D-MD) to observe, “It just goes to show how they’re making this up as they go.” Several officials invoked self-defense as a justification for using force without congressional or Security Council approval by claiming that Soleimani was killed to prevent an “imminent attack on U.S. forces.” The evidence to support this claim was simply not there, however. Within days, Attorney General Barr would confess that the “concept of imminence is something of a red herring.”

The U.S. government’s “official” justification for the strike then abandoned the notion that the strike was conducted as anticipatory self-defense against an imminent future threat and recast the U.S. attack as reactive self-defense in response to “an escalating series of armed attacks in recent months by the Islamic Republic of Iran and Iran-supported militias on U.S. forces and interests in the Middle East region” beginning in the summer of 2019. The Trump administration’s arguments in support of this justification are memorialized in: (1) a still heavily redacted OLC opinion dated March 10, 2020, two months after the strike, focused on the domestic statutory and constitutional grounds for the strike; (2) a letter to the United Nations Security Council dated Jan. 8, 2020 articulating the international law basis for the action; and (3) a report issued pursuant to Section 1264 of the 2018 National Defense Authorization Act that summarized both the international and domestic law bases for the strike.

The Trump administration cited “deter[ing] Iran from conducting or supporting further attacks against United States forces” and “degrad[ing] the Iran’s and Qods-Force-backed militias’ ability to conduct attacks” as elements of the self-defense justification for the strike under both the U.S. Constitution and international law. The administration also invoked the 2002 Authorization for the Use of Military Force (which the Biden administration has asked Congress to repeal) as domestic legal authority for the action.

The Dangers of the Soleimani Opinions

The dangers of the Soleimani legal opinions arise not from novel legal theories, but by how those opinions apply longstanding constitutional and international legal frameworks to reach unwarranted conclusions. The fundamental error in the opinions involves distorting these frameworks to fit inapposite facts. As a result, these legal justifications erode important constraints imposed by both the U.S. Constitution and the U.N. Charter on the unilateral use of force by the President in the future.

Why the Strikes Should Have Failed the “War in the Constitutional Sense” Test

Although the heavily redacted OLC opinion appears to apply the traditional “nature, scope, and duration” framework and pays lip service to the risk of escalation, the memo ultimately concludes that the “strike against Soleimani would not rise to the level of a war for constitutional purposes.” While the specific reasoning is not publicly available for analysis, it is not too far a stretch to say that OLC must have erred in reaching this conclusion, given that both the predictable and predicted risk of escalation from the strike would be inconsistent with previous applications of the “nature, scope, and duration” framework.

The risk of escalation from the killing of Soleimani was predictable because unlike a clandestine jihadi group such as al Qaeda, Iran is a state with significant military capabilities, notably including ballistic missiles. Iran, unlike the jihadi groups against which the United States had previously deployed decapitation strikes, could readily avenge itself on U.S. forces. The ability of Iran to retaliate against the United States for the attack on Soleimani was greater not only because of these military capabilities, but also because U.S. troops on the ground throughout the region were ready targets, a key fact that OLC has previously cited in weighing the risk of escalation.

Moreover, the executive branch itself had previously predicted escalation as a result of an attack on Soleimani. Former CIA official Doug London observed that “[i]ntelligence assessments on the anticipated escalatory paths Iran would follow in response to kinetic U.S. retaliatory measures have been consistent and well briefed to every [recent] president.” Indeed, both the Bush and Obama administrations had refrained from attacking Soleimani because they recognized the likelihood of escalation. Reflecting on the apparent lack of attention to the risks of escalation by the Trump team, former senior CIA official Marc Polymeropoulos wrote, “amongst my fellow retired operations officer colleagues from CIA — many of them at the senior intelligence service level — there was near unanimous shock at the strike.” Congresswoman Elissa Slotkin, a former CIA analyst and Pentagon official under both Bush and Obama, explained that “what always kept both Democratic and Republican presidents from targeting Soleimani himself was the simple question: Was the strike worth the likely retaliation, and the potential to pull us into protracted conflict?”

In fact, Soleimani’s killing, an overt attack on a senior military leader of state, led to the very sort of escalation, most notably the ballistic missile attacks on U.S. troops on the ground, which deprives Congress of its authority under the “declare war clause” according to the OLC’s own framework. As the serious injuries suffered by over 100 U.S. troops attest, it was by luck, not careful calculation by the Trump administration that there were no U.S. fatalities from Iran’s predictable counterattack. That hostilities did not escalate further was fortuitous and surprising, but by no means the most likely outcome.

The facts of the Soleimani attack and its foreseeable and foreseen aftermath render the subsequent OLC memo blessing the operation an outlier in the application of the “nature, scope, and duration” test. No other publicly available opinion has so minimized the risk of escalation, particularly given the capabilities of the adversary and presence of U.S. troops on the ground. Nevertheless, future administrations may now rely upon the Soleimani precedent to engage in escalatory military adventures in conflict with well-armed nation-state opponents (including possibly Iran) all while bypassing Congress and the necessary deliberation contemplated by the Declare War Clause. If OLC’s “nature, scope, and duration” framework does not bar an operation as patently risky as the attack on Soleimani, it is unlikely to stop very much at all and may become another functionally meaningless constraint like the national interest test.

Why the Strikes Should Have Failed the Self Defense Test

The Trump administration invocation of self-defense under international law distorts the concept beyond recognition. As a matter of customary international law, actions taken in self-defense must be both necessary and proportionate. As for the threshold requirement of necessity, the United States has explained, “the international law of self-defense requires that such uses of force be necessary to address the threat giving rise to the right to use force in the first place.”

The fundamental error in the opinions involves distorting the legal frameworks to fit inapposite facts.

The strike against Soleimani fails the test for self-defense because it was not necessary, in the sense that it did not address the threat giving rise to the right to use force in the first place. The killing of Soleimani did not mitigate the threats to U.S. forces purportedly motivating the operation: attacks by paramilitaries in Iraq and attacks by the Iranian military itself. Attacks by these paramilitary groups have not only continued, but increased in the years following Soleimani’s killing. And as evidenced by the subsequent ballistic missile attack on U.S. troops at al Assad (an attack unprecedent in scope and precision), killing Soleimani increased the threat to U.S. forces.

Perhaps the reason that the self-defense rationale for killing Soleimani is so strained is that this rationale was a pretext. According to extraordinary reporting by Jack Murphy and Zach Dorfman, “plans to kill the Iranian general date back to the early days of the Trump administration.” Reportedly, Pompeo and some other administration officials had pushed to kill Soleimani long before the attacks by Iran and Iranian-backed paramilitaries in 2019 that the United States cited in its Article 51 letter as the purported predicate for self-defense. According to this account, deliberations within the administration about killing Soleimani intensified in the summer of 2018 coinciding with the U.S. withdrawal from the Iran-nuclear deal. Victoria Coates, then NSC’s senior official for the Middle East complained that President Trump “wanted [military] options, but they were always watered down” by the Department of Defense. The New York Times also reported, in a deeply investigated piece, that the Trump administration discussed targeting Soleimani for 18 months prior to the eventual strike.  It thus appears that the Trump administration used the killing of a U.S. contractor by Iran-backed militias as a casus belli to launch an attack that some officials had long agitated and planned for.

In sum, there is great reason to conclude that the facts understood at the time did not come close to satisfying the necessity test.


Reducing the risk that the Commander in Chief will take the United States to war, including a regional armed conflict, on his or her own initiative requires, first and foremost, structural reform to rebalance the allocation of war powers between Congress and the President. Bipartisan legislation such as the Senate’s National Security Powers Act and its House equivalent, the National Security Reform and Accountability Act,  represents bold moves in that direction. Yet even if such a legislative overhaul is enacted, the President may be able to spuriously invoke “self-defense” to conduct an end run around Congress for discrete operations with significant escalatory potential.

To effectively mitigate the likelihood that future presidents will abuse their authority as Commander in Chief, including through reckless “one-off strikes” that drag the country into war, requires the executive branch to self-police properly. Indeed, administration lawyers would well serve their clients by repudiating extreme legal positions, as grossly flawed opinions deprive the executive branch’s internal legal framework of legitimacy. If the requirements for self-defense under domestic and international law and the “nature, scope, and duration” framework are to impose meaningful constraints on the use of force, then the executive branch must apply them rigorously.

In keeping with that imperative, the Department of Justice should rescind the Soleimani legal opinions and correct the record with the United Nations Security Council regarding the Trump administration’s letter. As a matter of legal threat reduction, the Soleimani opinions should be disavowed before another administration invokes them to justify another pretextual use of force. The responsibility for mitigating such a risk lies not only with decision makers in the future but also with those walking the halls of power now.


Brian Finucane (@BCFinucane) is senior adviser with the U.S. Program at the International Crisis Group and a Non-Resident Senior Fellow at the Reiss Center on Law and Security at NYU School of Law. Prior to joining Crisis Group in 2021, he served as an attorney-adviser in the Office of the Legal Adviser at the U.S. Department of State. Although he worked at the State Department at the time of the Soleimani strike, he was not involved in the operation or the formulation of the Trump administration’s legal justifications for the operation.