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How the 2002 Iraq AUMF Got to Be So Dangerous, Part 1: History and Practice

Scott R. Anderson
Tuesday, November 15, 2022, 12:24 PM

Congress originally enacted the 2002 AUMF to remove Saddam Hussein. But in the subsequent 20 years, it’s been used for so much more.

U.S. Army paratroopers prepare to board planes as part of Operation Iraqi Freedom (Tech. Sgt. Stephen Faulisi, U.S. Air Force,; United States Government Work,

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Editor's Note: This is the first in a two-part series on the history and interpretation of the Authorization for Use of Military Force Against Iraq Resolution of 2002, or 2002 Iraq AUMF. This article examines how the 2002 Iraq AUMF has been used throughout its 20 year history. Part two analyzes how the executive branch interprets the 2002 Iraq AUMF and the implications this has for its possible repeal.

For the past two years, Congress has been on the verge of a step that it hasn’t taken in more than half a century: the repeal of an outstanding war authorization. Several decades-old authorizations are nominally on the chopping block. But only one has been the subject of substantial debate: the repeal of the Authorization for Use of Military Force (AUMF) Against Iraq Resolution of 2002 that authorized the 2003 invasion of Iraq.

Legislation rescinding the 2002 AUMF was among the first House measures introduced in the 117th Congress in 2021. A few weeks later, the Senate reintroduced its own longstanding bipartisan proposal to repeal both the 2002 AUMF and the separate 1991 AUMF that authorized the first Gulf War. A bipartisan House majority voted 268-161 in support of repeal in the summer of 2021. The Biden administration even endorsed the move, providing assurances that it “would likely have minimal impact on current military operations,” as “the United States has no ongoing military activities that rely solely on the 2002 AUMF as a domestic legal basis.” And after holding an additional hearing on the matter, the Senate Foreign Relations Committee voted 14-8 to favorably report that chamber’s own repeal measure to the broader Senate a few months later.

But since then, progress on the proposal has flagged. Despite discussions among Senate leadership, the Senate proposal has yet to receive a floor vote. Last year, the House incorporated repeal into its version of the 2022 National Defense Authorization Act (NDAA), but the Senate did not, leading the conferees to omit it from the final version that was enacted into law. This year, the same scenario may yet repeat itself: while the House has included repeal in its version of the 2023 NDAA, it’s not yet clear whether a parallel measure will make its way through the complex NDAA process being pursued by the Senate. If it does not, then the robust bipartisan coalition of Senators supporting repeal will have to find another legislative vehicle—or make the difficult case that a freestanding bill warrants some of the extremely limited floor time both chambers have left before this Congress ends. Otherwise, they will have to start the process all over again when the 118th Congress sits in January next year.

Those who care about preserving Congress’s role in major decisions on war and peace should hope that proposals for repeal find a way forward. The Biden administration is undoubtedly correct that the 2002 Iraq AUMF is not necessary for any ongoing military operations and that, even without it, the president would retain the same robust ability to defend U.S. troops in Iraq that he employs in other dangerous corners of the world. But this doesn’t reduce repeal to a mere exercise in good housekeeping. 

The key question in weighing repeal is not what the 2002 Iraq AUMF does authorize, but what it could authorize. In the eyes of the executive branch, 20 years of interbranch practice has put an enabling gloss on the 2002 AUMF’s broad language that makes it a potential vehicle for military activity of nearly any type or scale so long as there is some nexus to Iraq. Such carte blanche authorization should be of deep concern to Congress, particularly when tied to a country that has a complex relationship with one of the United States’ most contentious rivals, Iran. And while there may be good reasons to question the validity of this interpretation, there are few signs that the federal courts or any other institution is willing and able to restrain a future president from relying on them, unless and until Congress itself acts.

For better or worse, the executive branch’s understanding of what the 2002 Iraq AUMF may be used for in the future is intimately tied up with the ways in which it has been used in the past—and how Congress has interacted with that history. For that reason, this article begins with a brief history that tracks the 2002 Iraq AUMF from its origins focusing on regime change in Iraq through its most recent use by the Trump administration and how the Biden administration has conceived of it since. The next piece in this series will pick up this history and lay out what use the executive branch makes of it.

Debate and Enactment

Congress enacted the Iraq AUMF in October 2002 at the request of the George W. Bush administration, which had spent much of the prior year building the case for a preemptive war against the Saddam Hussein regime in Iraq over its alleged possession of weapons of mass destruction. The stated intent behind the 2002 AUMF was not to immediately launch a war but to use the threat of force to pressure the Saddam Hussein regime into accepting a diplomatic solution, even as Secretary of State Colin Powell and others pressured the United Nations to take firmer action itself. That said, even at the time, many believed the Bush administration was set on regime change, by force if necessary.

The Bush administration had originally sought an arguably more open-ended authorization, but negotiations with Congress produced a final text that was a bit more constrained. Two-thirds of it is committed to a lengthy preamble that spells out various grievances against the Hussein regime before diverging into a brief discussion of the then-new global war on terrorism. The AUMF’s operative language, by contrast, is quite succinct, stating:

The President is authorized to use the Armed Forces of the United States as he determines to be necessary and appropriate in order to–

(1) defend the national security of the United States against the continuing threat posed by Iraq; and

(2) enforce all relevant United Nations Security Council resolutions regarding Iraq.

Before the President could rely on this authorization, however, he had to certify to Congress that “further diplomatic or other peaceful means” were no longer sufficient to accomplish this objective and then report to Congress on how he used the AUMF at least once every 60 days. This version ultimately passed with substantial bipartisan support, though most Democrats in the House and nearly half in the Senate—as well as a handful of Republicans—voted in opposition.

Of course, this wasn’t the first time Congress had legislated on the question of Iraq. Congress enacted another AUMF in January 1991 in order to “achieve implementation” of certain specified U.N. Security Council (UNSC) resolutions relating to Iraq. Subsequent congresses had since suggested that this authorization remained extant even after the end of the first Gulf War, and prior presidents had relied on it to impose “no-fly zones” over Iraq in 1992 and to launch military strikes against Iraq in both 1996 and 1998. As recently as 1998, Congress had also adopted legislation urging action against the Hussein regime for materially breaching Iraq’s international legal obligations and lent support to efforts to remove Hussein from power, though it expressly stopped short of authorizing any use of force for that purpose. And, just the prior year, the same Congress had enacted the 2001 AUMF, which authorized the use of “necessary and appropriate force against those…[who] planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001, or harbored such organizations or persons.” This law was already being cited as the domestic legal basis for military action against the Taliban and al-Qaeda in Afghanistan and elsewhere around the world, just as it is today.

For some within the George W. Bush administration, these prior actions raised the question of whether additional legislation was needed or even advisable. The Justice Department’s Office of Legal Counsel (OLC) went so far as to argue that, “to the extent that the President were to determine that military action against Iraq would protect [U.S.] national interests, he could take such action based on his independent constitutional authority” without needing further authorization from Congress. Congress’s prior enactments on Iraq strengthened the president’s case, it argued, while the 1991 and 2001 AUMFs could provide an alternate source of statutory authority if the president determined certain factual conditions had been met. While Bush ultimately decided to work with Congress, these alternative legal theories provided leverage in negotiations, limiting the extent to which some in Congress felt they could push back on the White House’s demands. They also informed the official statement that Bush issued upon signing the AUMF, which noted that his decision to pursue legislation “did not...constitute any change in the long-standing positions of the executive branch on...the President's constitutional authority to use force to deter, prevent, or respond to aggression or other threats to U.S. interests.”

By early 2003, it had become clear that Secretary of State Colin Powell’s efforts to persuade the UNSC to support a U.S.-led military operation to remove the Hussein regime had failed. Instead, the Bush administration determined that the United States would proceed on its own, alongside a coalition of willing allied nations. On March 18, 2003, President Bush issued the certification required by the AUMF, alongside a report that identified the 2002 Iraq AUMF—as well as the president’s authority under Article II of the Constitution and the 1991 Iraq AUMF—as providing the domestic legal grounds “to use force against Iraq to protect the security of the American people and to compel compliance with UNSC resolutions.” On March 21st, 2003, Bush provided a second notification to Congress pursuant to the War Powers Resolution of 1973 announcing his decision. But by that point, the war had begun, setting the stage for what would become nearly two decades of practice in interpreting and applying the 2002 AUMF’s terms.

Invasion and Occupation

Following two days of preparatory air strikes, coalition ground forces crossed Iraq’s southern border with Kuwait early in the morning on March 21st, 2003. While the bulk of early military engagements were with Iraq’s official armed forces, the invading troops met with surprisingly stiff resistance from regime-affiliated irregular forces and foreign fighters as well. They also came into occasional conflict with other armed groups that were operating to advance their own interests in the chaos of post-invasion Iraq, ranging from the idiosyncratic Iranian resistance movement Mujahedin-e Khalq to paramilitary forces associated with the Iranian government like the Badr Organization. As U.S. forces assumed control of Iraqi cities and territory, they also began to play a more active role in suppressing domestic violence and unrest, eventually going so far as to adjust their rules of engagement to permit the use of force for purposes ranging from the detention of criminal suspects to the prevention of property damage. 

President Bush declared an official end to major combat operations on May 1, 2003, at which point the United States and its main coalition partners shifted into a different role: that of occupying powers. Acting through the U.S.-controlled Coalition Provisional Authority (CPA), they assumed responsibility for a range of functions that would normally be performed by the now-deposed Iraqi government. This included national defense, with the commander of U.S. Central Command, who served as the head of the coalition military forces in Iraq, specifically being tasked with “deterring hostilities” and “maintaining Iraq’s territorial integrity and security.” 

The most immediate threat to Iraq’s security and stability, however, quickly proved to be internal. The removal of the Hussein regime and subsequent CPA decision to dissolve the Iraqi armed forces created a security vacuum that various armed groups soon stepped in to fill. As security conditions deteriorated, U.S. and coalition military forces took a lead role in military operations targeting both the armed remnants of the Hussein regime as well as various violent Salafi movements, some of which were linked to al-Qaeda. They also came into conflict with various Shi’a militias, which were believed to be major drivers of the brutal inter-sectarian violence that was rapidly enveloping the country. 

At times, these latter operations also implicated another, even more politically fraught element: agents of Iran, which had longstanding ties to many Shi’a political organizations in Iraq and provided various Shi’a militias with support through the paramilitary Quds Force within its Islamic Revolutionary Guard Corps (IRGC). IRGC personnel were detained in the course of operations against Shi’a militia groups as early as 2003, though most were eventually released. Over time, however, some U.S. military commanders began to view the IRGC as a hostile force actively fomenting instability against the U.S. military presence. By 2006, U.S. special operations forces were engaged in operations specifically intended to counteract IRGC activities and influence, including by targeting suspected IRGC officials for capture. The most well-known of these operations occurred in January 2007, when U.S. special operations forces attempted to capture several senior Iranian officials who were visiting with Iraqi President Jalal Talabani in the city of Erbil. While the operation missed its intended targets, it ended in a raid on an Iranian liaison office and the capture of five Iranian officials who were alleged to be IRGC agents. Some of the detained officials remained in U.S. custody through 2009, over objections by both Iraqi and Iranian officials who claimed that the office was—or had been in the process of becoming—a legitimate diplomatic mission.

Despite widespread misgivings about the U.S.-led invasion of Iraq, the UNSC recognized the United States and its coalition allies as occupying powers in late May 2003, after the United States and United Kingdom formally acknowledged that status and accepted the resulting international legal obligations. By October 2003, the deteriorating security situation in Iraq led the Security Council to authorize “a multinational force under unified command to take all necessary measures to contribute to the maintenance of security and stability in Iraq,” a role that coalition military forces soon filled. This mandate continued even after the formation of a new Iraqi interim government in June 2004, though it was made contingent on consent from Iraq’s new political leadership, which asked that the multinational forces in Iraq remain present in part to combat “forces in Iraq, including foreign elements, that are opposed to our transition to peace, democracy, and security” and to support “the defence of Iraq’s land, sea and air space.” This mandate was subjected to periodic review and repeatedly renewed until finally coming to an end in December 2008. The Security Council later revoked most of the other extraordinary obligations it had imposed on Iraq through resolutions the following year, except for a lingering few that largely related to the first Gulf War.  

As the end of the U.N. mandate approached, the United States and Iraq negotiated a bilateral security agreement that authorized U.S. forces to remain in Iraq through the end of 2011, but with a reduced footprint and limited scope of operations that was more closely bound to Iraqi oversight. Pursuant to this new arrangement, coalition forces spent the first half of 2009 transferring most day-to-day security responsibility around the country to Iraqi forces. Non-U.S. elements of the multinational force exited the country, leaving the U.S. forces in Iraq as the inheritors of the coalition forces’ responsibilities under the security agreement. The United States—now under the leadership of the Obama administration—still routinely engaged in military operations against armed groups like al-Qaeda in Iraq in coordination with Iraqi forces. And while Iraqi officials were often more reticent to approve operations against Shi’a militias, many of which had ties to Iraq’s Shi’a-led government, some such operations did take place, both in coordination with Iraqi authorities and, in a few rare cases, independent of them. The United States also continued to operate detention facilities in Iraq through the summer of 2010, as it gradually transferred the approximately 22,000 detainees it still had in its custody to Iraqi control. Even then, the United States retained custody of a small group of high-value detainees as it tried to secure adequate assurances regarding their continued detention prior to transfer. 

Throughout this period, the executive branch appears to have operated on the understanding that most, if not all, of these activities were—and continued to be—authorized by the 2002 Iraq AUMF. Ambassador David Satterfield, who was then serving as Coordinator for Iraq at the U.S. Department of State, communicated as much in congressional testimony he gave in October 2008, wherein he expressed the executive branch’s views that the authorization provided by the 2002 AUMF “remains in effect past the end of the Chapter 7 mandate[,]” noting:

“[T]he Congress authorized the President to use force in Iraq for two reasons, to enforce U.N. Security Council resolutions and to defend the national security of the United States against the continuing threat posed by Iraq. Now, at the time of the resolution, the Saddam Hussein regime was the primary threat posed by Iraq. But the Congress recognized it was not the only threat; and, in particular, al-Qaeda had a presence in Iraq. The situation in Iraq continues to present a threat to United States national security even after the fall of the Hussein regime….”

Consistent with this view, none of the above engagements resulted in the 48 hour reports that the War Powers Resolution requires if the president were acting pursuant to his Article II authority, even though both the George W. Bush and Obama administrations generally released those reports publicly in other cases not covered by AUMFs. Moreover, while some activities theoretically may have been tied to the enforcement of UNSC resolutions authorized by both the 1991 and 2002 AUMFs, the fact that so many U.S. military activities continued even after the UNSC closed out nearly all of Iraq’s outstanding obligations suggests that this was not the primary legal grounds for U.S. activities either. Instead, the main legal grounds appeared to be, as Satterfield paraphrased in his testimony, the 2002 AUMF’s language providing “authorization to defend the national security of the United States against the continuing threat posed by Iraq.”

After Withdrawal

The security agreement was set to expire by its own terms at the end of 2011, and efforts to negotiate a follow-on agreement had largely failed by the fall of that year. As it became apparent that there would be no follow-on agreement, U.S. forces began an expeditious withdrawal from the country, transferring various facilities and equipment either to the Iraqis or the U.S. Embassy in Baghdad, which assumed primary responsibility for the bilateral relationship. By the time the withdrawal was complete, the only major military contingent remaining in-country was a large Office of Security Cooperation (OSC) that operated from within the embassy and oversaw the various forms of security assistance the United States was continuing to provide to its Iraqi partners. But the OSC had its own separate statutory authorities. From the completion of the 2011 withdrawal onward, the Obama administration made clear that it was no longer relying on the 2002 AUMF. By July 2014, then-National Security Advisor Susan Rice even went so far as to urge its repeal on the logic that it was no longer needed.

That endorsement, however, proved ill-timed. Within weeks, an offensive led by the Islamic State in Iraq and the Levant (ISIL)—which had been percolating in northwestern Iraq and adjoining parts of war-torn Syria for months—pushed deep into Iraqi territory, threatening the cities of Baghdad and Erbil, both of which housed major U.S. diplomatic presences. The Obama administration intervened with airstrikes in August 2014, acting pursuant to the president’s Article II constitutional authority and in coordination with the Iraqi government, which had actively sought assistance from the United States and others in the international community. But as the possible end of the initial 60-day window for pursuing military action without congressional authorization imposed by the War Powers Resolution drew near, the White House advanced two statutory legal justifications for what was becoming a broader and more sustained U.S.-led military campaign: first, that ISIL, as a successor group to al-Qaeda in Iraq, fell within the scope of the 2001 AUMF and thus could be targeted in the same manner as other al-Qaeda affiliates around the world, including in both Iraq and Syria; and second, that the 2002 AUMF also provided a legal basis for actions against ISIL in Iraq and perhaps, in certain circumstances, in Syria. The Obama administration was careful to make clear that it viewed this latter authority as supplemental and redundant, to the point that it continued to support repeal of the 2002 AUMF and unsuccessfully sought more specific authorization from Congress. But the 2002 AUMF had nonetheless found application on a new battlefield that extended beyond Iraq’s borders. 

The Obama administration provided its fullest explanation of this 2002 AUMF argument in April 2015, when Defense Department General Counsel Stephen Preston gave a speech describing the legal framework for counter-ISIL operations. While most of his remarks focused on the 2001 AUMF, he briefly digressed to discuss the 2002 Iraq AUMF as well, stating: 

Although the threat posed by Saddam Hussein’s regime in Iraq was the primary focus of the 2002 AUMF, the statute, in accordance with its express goals, has always been understood to authorize the use of force for the related purposes of helping to establish a stable, democratic Iraq and addressing terrorist threats emanating from Iraq. After Saddam Hussein’s regime fell in 2003, the United States, with its coalition partners, continued to take military action in Iraq under the 2002 AUMF to further these purposes, including action against [al-Qaeda in Iraq], which then, as now, posed a terrorist threat to the United States and its partners and undermined stability and democracy in Iraq. Accordingly, the 2002 AUMF authorizes military operations against ISIL in Iraq and, to the extent necessary to achieve these purposes, in Syria.

In December 2016, this same language found its way into a footnote in the outgoing Obama administration’s capstone report outlining the legal and policy frameworks for the use of military force. The fact that the 2002 AUMF only appeared here and not in the text of the report underscores the limited role it was viewed as playing in ongoing military operations at the time. Yet this distillation of 13 years of practice would prove consequential, particularly after the Obama administration left office.

The Trump administration did little to upset this status quo during its first several years in office. Early on, the administration came out in opposition to any repeal or reform of either the 2001 or 2002 AUMFs, on the grounds that, as Acting General Counsel of the U.S. Department of Defense William Castle relayed in a 2017 speech, doing so “would cause unnecessary policy and legal uncertainty.” In March 2018, the administration provided a statutorily required update to the legal and policy frameworks report published by the Obama administration that reiterated Preston’s description of the scope of the AUMF and made explicit the previously implicit understanding that, while the 2002 AUMF “limits the use of force to address threats to, or stemming from, Iraq, it (like the 2001 AUMF) contains no geographic limitation on where authorized force may be employed.” As the Trump administration’s “maximum pressure” campaign against Iran escalated, there were growing concerns that it might try to use the 2002 AUMF (or other legal authorities) to justify military action against Iran. A bipartisan majority in the House and Senate even went so far as to vote in favor of a statutory provision that would have set limits on Trump’s ability to pursue military action against Iran, though the measure failed to advance due to the Senate’s supermajoritarian requirement to break a filibuster. For the time being, however, the Trump administration seemed content to employ the 2002 AUMF for the same limited purposes as the Obama administration, namely as redundant authorization for the ongoing military campaign against ISIL and little else.

This changed in December 2019, however, when the Trump administration chose to pursue airstrikes in both Iraq and Syria against Kata’ib Hezbollah, a prominent Iran-backed Shi’a militia that had been nominally incorporated into Iraq’s security forces yet continued to operate independently and was believed to be responsible for rocket attacks on U.S. personnel engaged in ongoing counter-ISIL operations and other activities in the country. While it did not offer a clear articulation of the legal basis for these actions at the time, the Trump administration had suggested in correspondence with Congress earlier in the year that both the 2001 and 2002 AUMFs authorized the use of force “as may be necessary to defend U.S. or partner forces” engaged in missions under those AUMFs, including the ongoing counter-ISIL mission in Iraq and Syria. (The Trump administration had previously relied on this “ancillary self-defense” argument to justify airstrikes against non-ISIL targets in Syria affiliated with the Assad regime that had threatened the counter-ISIL coalition’s on-the-ground allies, but only in relation to the 2001 AUMF.) In a later war powers report, the Trump administration confirmed that this was the domestic legal justification for both the December 2019 airstrikes against Kata’ib Hezbollah as well as subsequent airstrikes that it pursued against Iran-backed militias in both Iraq and Syria over the course of 2020.

But these actions were soon eclipsed by another, more consequential event: the Jan. 2, 2020 drone strike that killed IRGC commander Qassem Soleimani and much of Kata’ib Hezbollah’s senior leadership on the grounds of Baghdad’s international airport. The Trump administration once again initially demurred on providing a public legal justification for its actions, but ultimately provided Congress with a war powers report, arguing that its actions were permissible under the president’s Article II authority and the 2002 AUMF. The Trump administration did not, however, rely on the ancillary self-defense argument that it had deployed in relation to prior strikes on Iraqi militias. Instead, as U.S. Department of Defense General Counsel Paul Ney made clear in a March 2020 speech, Soleimani himself was viewed as “a necessary and appropriate target for the President to use force against under the 2002 AUMF” because of his role “as the leader of the Qods Force directly orchestrating hostilities against U.S. personnel and property in Iraq.” (Ney’s speech in turn closely paralleled an April 2020 OLC opinion justifying the Soleimani strike, a heavily redacted version of which was only made public through litigation in 2021.) Congress responded to the Soleimani strike by passing a joint resolution asserting in part that the 2001 and 2002 AUMFs “do not serve as a specific statutory authorization for the use of force against Iran” with bipartisan majorities in both chambers. President Trump, however, ultimately vetoed this resolution and its supporters in Congress were unable to secure the two-thirds support necessary in both chambers to override.

For its part, the Biden administration has, thus far, avoided relying on the 2002 AUMF. While the administration has pursued multiple airstrikes against Iran-backed militias in both Iraq and Syria, related war powers reports rely solely on the president’s Article II authority to do so and make no mention of any AUMFs. Other military activities pursued as part of the ongoing counter-ISIL campaign in Iraq and Syria continue to be justified through both the 2001 and 2002 AUMFs, but do not rely on the latter. Just a day in advance of the June 2021 House vote on repeal, the administration released a statement confirming its view that the 2002 AUMF was redundant with the 2001 AUMF in relation to all ongoing military operations and urging repeal. Biden administration officials later reiterated these same positions in an August 2021 hearing before the Senate Foreign Relations Committee

The same hearing, however, also revealed points of continuity in the executive branch’s views of the 2002 AUMF. The participating officials confirmed that the Biden administration continues to accept the theory of “ancillary self-defense” articulated by the Trump administration in relation to both AUMFs and verified (without endorsing) the Trump administration’s position that the Soleimani strike could also have been legally justified on the basis of the president’s Article II constitutional authority alone, without the 2002 AUMF. Two annual war power reports that the Biden administration is obligated to file with Congress on changes in the legal framework it sees as governing the use of military force—or at least those unclassified portions made available to the public—similarly noted no changes in its interpretation of the 2002 AUMF. Hence, while the Biden administration hasn’t been inclined to rely on the 2002 AUMF, it’s also not clear that it interprets it substantially differently from its predecessors. Nor has it taken any steps to repudiate these views that might make them less available to subsequent presidential administrations, other than to support repeal.

* * *

Most Americans and members of Congress understood that the 2002 Iraq AUMF was enacted to address the perceived threat posed by the Hussein regime in Iraq. But over the past 20 years, its mandate to “defend the national security of the United States against the continuing threat posed by Iraq” has been read to mean far more than that. As regime change in Iraq became an occupation, the AUMF came to authorize not just war on the Hussein regime but the assumption of responsibility for Iraq’s internal and external security following that regime’s removal. This in turn came to mean that it authorized the use of force against terrorists and other armed groups operating in Iraq—including, in some limited cases, suspected agents of Iran. This mission outlived the occupation and even the initial U.S. military operation itself, and eventually became a legal basis for an entirely new military campaign against ISIL in both Iraq and nearby Syria. But the old understanding that the AUMF authorizes the president to act as he sees fit to defend U.S. forces and advance stability in Iraq did not go away, and ultimately reemerged as a legal basis for the air strike that killed IRGC commander Qassem Soleimani.

Importantly, these actions also took place in full view of Congress. As the second piece in this series will explore, such practice has special significance in the eyes of the executive branch. Where Congress continues to knowingly fund and support activities pursued under a broadly worded authorizing statute, the executive branch often views this as congressional acquiescence to that interpretation. This approach has played an instrumental role in the gradual expansion in how the 2002 Iraq AUMF has been used—and it’s essential to understanding how the AUMF may be used in the future, if Congress chooses to leave it on the books.

Scott R. Anderson is a fellow in Governance Studies at the Brookings Institution and a Senior Fellow in the National Security Law Program at Columbia Law School. He previously served as an Attorney-Adviser in the Office of the Legal Adviser at the U.S. Department of State and as the legal advisor for the U.S. Embassy in Baghdad, Iraq.

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