Armed Conflict Congress Foreign Relations & International Law

How the 2002 Iraq AUMF Got to Be So Dangerous, Part 2: Interpretation and Implications

Scott R. Anderson
Tuesday, November 29, 2022, 8:01 AM

Repeal isn’t just good housekeeping. It would help ensure that Congress weighs in before pursuing another major war in the Middle East.

American soldier during firefight in Adhamiyah, Baghdad (Operation Phantom Thunder). (Source: US. Army photo by Sgt. Michael Pryor, 2nd Brigade Combat Team, 82nd Airborne Division Public Affairs, Public domain, via Wikimedia Commons.)

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Editor's Note: This is the second 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. Part one examines how the 2002 Iraq AUMF has been used over its 20-year history. This article analyzes how the executive branch has come to interpret the 2002 Iraq AUMF and what this means for its potential repeal.

By most accounts, when Congress enacted the Authorization for Use of Military Force (AUMF) Against Iraq Resolution of 2002, it was authorizing the George W. Bush administration to go to war with the Saddam Hussein regime in Iraq. But as the first article in this series documented, use of the 2002 Iraq AUMF did not stop there. Over the subsequent two decades, its language authorizing the use of the U.S. armed forces to “defend the national security of the United States against the continuing threat posed by Iraq” was used not just to remove the Hussein regime but also to facilitate the subsequent occupation of Iraq, including the assumption of responsibility for Iraq’s internal and external security. After the occupation ended, it was cited as the legal basis for an array of similar activities in support of the new Iraqi government, most notably its efforts at combatting al-Qaeda-associated terrorist groups. These efforts ended after the U.S. withdrawal in 2011 but were revived in 2014 when the Obama administration once again intervened in Iraq to lead a military campaign against the Islamic State in Iraq and the Levant (ISIL) terrorist group. The Trump administration in turn implemented a broader campaign against Iran-backed militias in Iraq and even against agents of Iran itself. All of this has been framed as falling within the scope of what the executive branch has consistently described as the 2002 Iraq AUMF’s dual purposes: “helping to establish a stable, democratic Iraq and addressing terrorist threats emanating from Iraq.”

This article examines the interpretive framework that has allowed the executive branch to read the 2002 Iraq AUMF so broadly. In recent years, the executive branch has increasingly justified its interpretations of both the 2001 AUMF—which separately authorizes military operations against the perpetrators of the Sept. 11 attacks, and provides the domestic legal basis for most global counterterrorism operations—and the 2002 Iraq AUMF in terms of its own historical practice. Specifically, it has argued that, where Congress is aware that the executive branch has advanced or acted upon a particular interpretation of the AUMFs, any legislation that appropriates funds for or otherwise engages in those activities serves to confirm Congress’s acceptance of the validity of that interpretation. Viewed through this lens, the 2002 Iraq AUMF becomes an exceptionally broad congressional authorization to use military force so long as there is some relation to Iraq. And while there are ample grounds for criticizing this approach, the fact that it has endured across presidential administrations of both political parties and in spite of legal challenges in the courts suggests that it is unlikely to go away any time soon.

Congress must bear this framework and the interpretations it leads to in mind as it debates the possibility of repeal. Concerns that repeal will limit the executive branch’s ability to confront Iranian militias and other actors threatening U.S. diplomatic and military personnel are misplaced, as the president has substantial authority to act in defense of U.S. personnel and facilities even without statutory authorization. Instead, what repeal will limit is future presidents’ ability to go beyond limited military action and engage in another major war in the Middle East without consulting Congress, which the 2002 Iraq AUMF—as currently interpreted by the executive branch—could readily be read to authorize. While the Biden administration seems unlikely to stretch the 2002 Iraq AUMF to this potential upper bound, future presidents might view the issue differently, especially given Iraq’s complex and often challenging relationship with its neighbor Iran. Nor is it clear whether the Biden administration and federal courts are able and willing to do anything to prevent this from happening unless Congress acts first. 

Historical Practice and AUMF Interpretation

The idea that subsequent practice should bear on how one interprets a statute is, in many ways, a strange one. Modern courts often use such practice to interpret other types of legal texts, such as contracts and treaties, but not statutes enacted by Congress. When interpreting statutes, courts instead look first and foremost to the text of the statute and then potentially to legislative history where the meaning of that text is unclear or otherwise not dispositive. Executive branch views are sometimes cited as confirmation of interpretations based on other grounds and may be entitled to interpretive deference in certain contexts. But the focus is otherwise generally on the intent of the Congress that enacted the statute, not the actions of those who implement the statute afterward.

Subsequent practice does, however, play a central role in how the executive branch approaches the president’s authority to use military force in a variety of other contexts. In discussing the scope of the president’s constitutional authority to use military force absent any congressional authorization, for example, recent presidential administrations have routinely maintained that “historical practice is an important indication of constitutional meaning” as it “reflects the two political branches’ practical understanding … of their respective roles and responsibilities with respect to national defense[.]” Over time, persistent practice can in turn put a “historical gloss” on how the Constitution is understood to distribute authority. As discussed further below, the executive branch specifically argues that, in the case of war powers, this gloss confirms that the president has broad authority to use military force absent express authorization from Congress, even though the Constitution gives Congress the authority “[t]o declare War.”

The executive branch has also argued that “Congress [can] authoriz[e] and ratif[y] executive branch action through appropriations measures” and other subsequent legislation adopted after the fact, so long as it has the requisite intent to do so. For example, in a 2000 opinion by the Justice Department’s Office of Legal Counsel (OLC) justifying military intervention in Kosovo, the executive branch asserted that “where the President has requested an appropriation in order to continue military operations, evidence showing that Members of Congress were specifically aware of the purposes of the appropriation request will tend to show that Congress intended to authorize continuing military operations[.]” (In the same opinion, OLC also rejected the validity of a provision of the 1973 War Powers Resolution that prohibited Congress from implicitly authorizing the use of force through appropriations and similar measures, on the grounds that one Congress cannot restrict how a future Congress chooses to exercise its legislative authority.)

The executive branch approaches the AUMFs through a combination of these two lenses. Specifically, it has argued that Congress has functionally ratified executive branch interpretations of the AUMFs by knowingly enacting subsequent legislation that appropriates funds for or authorizes activities premised on those interpretations. Of course, this is just one interpretive tool of many that the executive branch applies to the AUMFs. But as use of the two AUMFs has accumulated over their 20-year history, interpretations rooted in past practice have taken on greater significance—especially for the 2002 Iraq AUMF.

The executive branch has made similar arguments about implicit congressional approval since at least the 1970s, if not earlier. But this approach is perhaps most clearly spelled out in the Obama administration’s December 2016 report on the legal and policy frameworks guiding the executive branch’s use of military force and related activities. That report defended the executive branch’s position that the 2001 AUMF extended to ISIL by noting that “Congress has repeatedly and specifically funded the President’s military operation against ISIL through an unbroken stream of appropriations over multiple years.” It observed that Congress had also enacted other legislation contingent on the application of the 2001 AUMF to ISIL, including authorizations for “lethal and nonlethal assistance to select groups and forces fighting ISIL in Iraq and Syria.” Perhaps most importantly, Congress did so while engaging in “close congressional oversight of the status and scope of U.S. counter-ISIL activities, and with knowledge of the specific measures the President was taking to counter ISIL and the statutory provisions under which he was acting.” Together, the report concluded, these measures “convey Congress’s support for the President’s use of force against ISIL, including his determination that he had and continues to have authority to act under prior congressional authorizations for the use of military force.” 

In an endnote, the report also applied this same interpretive framework to the 2002 Iraq AUMF. Echoing earlier statements by officials in the Bush and Obama administrations, among others discussed in the prior piece in this series, it states:

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 dual purposes of helping to establish a stable, democratic Iraq and of addressing terrorist threats emanating from Iraq. After Saddam Hussein’s regime fell in 2003, the United States continued to take military action in Iraq under the 2002 AUMF to further these purposes, including action against [al-Qaeda in Iraq] (now known as ISIL). Then, as now, that organization posed a terrorist threat to the United States and its partners and undermined stability and democracy in Iraq. Congress ratified this understanding of the 2002 AUMF by appropriating billions of dollars to support continued military operations in Iraq between 2003 and 2011. 

The Trump administration later reiterated this understanding of the 2002 Iraq AUMF in its own related 2018 war powers report, while expressly adding the (previously implicit) caveat that, “although the Iraq 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.”

By some measures, this interpretive approach may be seen as relatively conservative compared to possible alternatives. At a minimum, it does not lend itself to novel applications that do not have some analogy in prior practice that was arguably ratified by congressional action, though other interpretive tools might fill this gap. And the executive branch is not arguing that subsequent appropriations and other legislation enactments provide independent statutory authorization for military action, as it did in relation to Kosovo—meaning that the plain language of the AUMFs themselves may still impose constraints on what the executive branch can read them as authorizing.

But in the specific case of the 2002 Iraq AUMF, these limits appear to be few and far between. As documented in the first article in this series, the 2002 Iraq AUMF has been cited as authorization for an incredibly broad and diverse array of military activities over its 20-year history, all in full view of—and using funds repeatedly appropriated by—Congress. And the AUMF’s plain language imposes few clear limits on the executive branch, aside from requiring a certification that the George W. Bush administration issued in 2003 and imposing certain reporting requirements. The Trump administration implied as much in its 2020 OLC opinion justifying the January 2020 strike that killed Qassem Soleimani, an Iranian official who headed the Islamic Revolutionary Guard Corps’ (IRGC’s) paramilitary Quds Force, as well as the leadership of the Iraqi militia group Kataib Hezbollah. Specifically, OLC emphasized the deferential language the 2002 AUMF uses in authorizing the use of the armed forces “as [the president] determines to be necessary and appropriate in order to … defend the national security of the United States against the continuing threat posed by Iraq” (emphasis in original). For the purposes of the Soleimani strike, OLC concluded that it was sufficient that the executive branch believed “the Qods Force [that Soleimani headed] would continue to undermine stability in Iraq and continue to threaten U.S. personnel in Iraq” and that the operation targeting him “was narrowly tailored to Soleimani’s presence in Iraq and to his support to and direction of militias operating in Iraq.” Given the Trump administration’s clear statement elsewhere that the 2002 Iraq AUMF imposes no geographic limitations, this is best read as requiring some nexus to Iraq as opposed to a requirement that uses of force occur within Iraq.  Whatever such a nexus might look like, the requirement for one appears to be the main constraint that the executive branch sees on the 2002 AUMF’s authorization for the use of force to address threats to the stability of Iraq or from terrorist groups operating there.

Congress may also have imposed another limitation in April 2020, when bipartisan majorities in the House and Senate enacted a joint resolution directing a withdrawal of U.S. armed forces from hostilities with Iran. It included a finding that the 2002 AUMF “do[es] not serve as a specific statutory authorization for the use of force against Iran.” At a minimum, the adoption of this statement by a majority in both chambers of Congress makes it much harder for the executive branch to argue that Congress has uniformly acquiesced to its prior suggestions that the 2002 AUMF might reach Iran. But this statement also appears in the nonbinding “findings” section of the resolution. And the joint resolution itself was vetoed by then-President Trump and never enacted into law. As a result, the extent to which the executive branch (or the courts) will view this resolution as constraining possible applications of the 2002 Iraq AUMF against Iran moving forward is unclear.

To date, no federal court has passed judgment on the executive branch’s interpretations of the scope of applicability of the AUMFs. Federal courts have been notoriously reticent to weigh in on war powers questions in recent decades and have often used flexible justiciability standards and other doctrinal tools to avoid reaching the merits of legal challenges that raise them. This remains true even though the Supreme Court has arguably narrowed the scope of one of the main non-justiciability doctrines invoked in earlier war powers cases, the political question doctrine, by suggesting that the political question doctrine should not apply where the president acts contrary to a statute enacted by Congress.

In line with this practice, the only two significant legal challenges that have been brought against the 2001 and 2002 AUMF interpretations underlying the counter-ISIL campaign in Iraq and Syria have concluded without ever reaching the merits. In Smith v. Obama—a lawsuit launched by a U.S. service member set to deploy to Syria—the district court declined to reach the merits on justiciability grounds, while the U.S. Court of Appeals for the D.C. Circuit held the matter on its docket for more than a year until the plaintiff’s military commitment ended, at which point it dismissed the case as moot. Meanwhile, in Doe v. Mattis—a legal challenge launched by a U.S. national being detained by a U.S. partner group in Syria on suspicion of being a member of ISIL—the district court issued an order requiring that the government notify it before transferring the plaintiff (that was in turn upheld by the D.C. Circuit) but otherwise allowed the matter to remain in process for over a year without resolution, until the plaintiff and U.S. officials agreed on a disposition that similarly mooted the case. (Notably, the Obama and Trump administrations both deployed arguments relating to subsequent practice and congressional ratification in these matters.)

Whether deliberately or not, these justiciability barriers reinforce the executive branch’s interpretive approach by insulating executive branch interpretations of the AUMFs from judicial review absent a clear sign of congressional disagreement. Citing an array of federal court opinions adopting a similar approach that date back to the 1970s, the district court in Smith v. Obama drove this point home, stating:

Plaintiff has not pointed the Court toward any action that Congress has taken since the beginning of [the counter-ISIL campaign] that would indicate that Congress believes that further specific authorization (beyond the 2001 and 2002 AUMFs relied on by President Obama in his communications with Congress) is required …. This lack of conflict is relevant to the justiciability of Plaintiff's claims under the political question doctrine because judicial intervention into military affairs is particularly inappropriate when the two political branches to whom war-making powers are committed are not in dispute as to the military action at issue ….

… Congress is vested with considerable power to restrain the President in the conduct of military operations …. Such powers may not always be sufficient, and judicial intervention may be necessary when they fail. But in this case, where these powers have not been exercised and there does not appear to be any disagreement between the two political branches as to the legality of a live military operation, the Court finds it inappropriate to inject itself into these affairs.

Under this logic, executive branch interpretations of AUMFs are justiciable only where there are clear signs that Congress disagrees with them—a standard that, not coincidentally, aligns with a focus on subsequent practice and congressional acquiescence when interpreting AUMFs. In this sense, the executive branch’s interpretive approach may be best understood less as a method of statutory interpretation and more as a strategy for keeping the executive branch within the range of interpretations that federal courts are unlikely to subject to judicial scrutiny. 

There are good reasons to be skeptical of this interpretive approach. At a minimum, it’s a departure from the normal methods of statutory interpretation and their focus on text and intent—a point driven home by many critiques of the executive branch’s broad readings of the AUMFs. If anything, it employs a logic that is closer to that of the Youngstown framework that federal courts often use to evaluate claims of executive branch authority, which ties the validity of such claims to the extent to which the executive branch is acting consistent with “the expressed or implied will of Congress.” The strong implication is that, at least when it comes to uses of military force, broader separation of power concerns outweigh the quotidian concerns of conventional statutory interpretation—an implicit case for applying an exceptional standard to war-related questions that may strike some as hard to swallow, if not downright dangerous.

These reservations notwithstanding, however, the executive branch’s interpretive approach does more or less align with general judicial practice, outlining the range of potential interpretations that are least likely to face legal pushback, even if they strain the usual bounds of credibility. For these reasons, it’s perhaps not surprising that such interpretations continue to be put forward as an option—with, no doubt, some warnings and caveats—by executive branch lawyers who understand their primary responsibility to be to advise policymakers on how to advance their preferred policy goals in a legally defensible manner, not to restrain those options to what they understand to be the best view of the law. Nor is this tendency likely to decline now that this interpretive approach has been employed across presidential administrations of both parties, in full view of Congress and the broader public. Instead, how the executive branch makes use of subsequent practice in interpreting the AUMFs is simply a reality that Congress must take into account when it enacts such pieces of legislation—and debates their later modification or repeal.

Implications for Repeal

This framework helps explain how the executive branch has used the 2002 Iraq AUMF in the past. More importantly, it may also help anticipate how it may yet be used in the future. This is the most important consideration for Congress as it weighs repeal, as it sheds light on how repeal will likely impact military operations that future presidents will otherwise see themselves as having the legal authority to pursue. And for the 2002 Iraq AUMF in particular, the impact of repeal is both less and, in important ways, far more than some may anticipate.

Even absent an AUMF or other statutory authorization, the executive branch has long maintained that the president has the independent constitutional authority to use military force to defend the United States and its nationals—including its diplomatic and military personnel—from attacks and the imminent threat thereof. For these reasons, repeal of the 2002 AUMF would not—as the Biden administration has repeatedly emphasized in its own strikes on Iran-backed militias in Iraq and Syria, which it has premised on this Article II authority—leave U.S. personnel in Iraq undefended; to the contrary, the president would have the same substantial authority to defend them from attack as he has to defend U.S. personnel in various other hostile corners of the world.

Nor would repeal of the 2002 Iraq AUMF necessarily prevent presidents from taking limited action in defense of U.S. partner forces or even to advance Iraqi stability, if a president believed that doing so was in the national interest of the United States. While the issue continues to be hotly debated, recent presidents of both political parties have also argued that Article II of the Constitution gives them the independent constitutional authority to direct the use of military force in pursuit of various other U.S. national interests.

The main limitation to this Article II authority—acknowledged as a possibility in OLC opinions issued by presidential administrations of both parties—is that the “anticipated nature, scope, and duration” of any resulting use of military force must be limited, so that it falls below the threshold of a war requiring congressional authorization under the Constitution’s Declare War Clause. Where exactly this threshold lies is unclear. No court has ever encountered the question, and the executive branch’s analyses generally incorporate an inconsistent array of case-specific factors in ways that are designed to justify executive branch action more than subject it to meaningful scrutiny. Past presidents have pursued substantial armed conflicts on the basis of similar claims of authority; the Korean War often serves as the “high water mark” for this standard, if not an example of a case that may well have exceeded it. (Some observers have also suggested that this limitation might not apply in at least some cases of national self-defense, citing OLC opinions from shortly after the Sept. 11 attacks that do not acknowledge it.) Regardless, the contemporary understanding has generally been that Article II-based uses of force risk crossing this threshold where they involve “prolonged and substantial military engagements, typically involving exposure of U.S. military personnel to significant risk over a substantial period,” or where they pose a significant risk of escalating into such a conflict. In other words, while presidents can deploy the armed forces for a variety of purposes on their own authority, the one thing they cannot do without Congress is commit the United States to a major war.

This constitutional limitation on a president’s ability to initiate major conflicts is in turn reinforced by the 1973 War Powers Resolution, which further requires that presidents not only report to Congress within 48 hours when they deploy U.S. armed forces into hostilities without congressional authorization but also end U.S. participation in those hostilities within 60 to 90 days if Congress does not authorize it after the fact. While past presidents have occasionally questioned the constitutionality of this withdrawal requirement, more recent administrations have seemed to acknowledge its likely validity. None to date have proved willing to ignore this requirement outright, though several have employed narrow interpretations of the term “hostilities” and other strategies for evading it

The main effect of the 2002 Iraq AUMF—and other similar authorizations for the use of force—is that it provides an escape hatch from these limitations on major war, both constitutional and statutory. By relying on the statutory authorization provided by the 2002 AUMF, the executive branch could in theory pursue a conflict of any type or scale—and involving any risk of escalation—without being limited by the Declare War Clause or triggering the War Powers Resolution 60- to 90-day withdrawal requirement. The only limitations would be those that the executive branch recognizes as being imposed by the 2002 AUMF itself—namely, that it be intended to advance the stability of Iraq or protect U.S. or partner forces operating there and have some nexus to Iraq itself. 

In other contexts, such limitations might be enough to constrain U.S. action and prevent further entanglement in a major conflict. But this is simply not the case with Iraq. Cultural, economic, and historical ties, as well as geographic proximity, closely link events in Iraq to its neighbor, the Islamic Republic of Iran. Yet Iran is also a major U.S. rival, as underscored by the recent “maximum pressure” sanctions campaign leveled against it by the Trump administration. In recent years, Iran has also pursued a broad campaign of interference in Iraq, including by undermining its governmental institutions and supporting various armed militias that have come to operate with relative impunity in much of the country. The same militias have also been involved in attacks on U.S. diplomatic and military personnel, the tempo of which has tended to reflect the state of broader U.S.-Iranian relations. Given these facts, it will not be hard for an executive branch intent on pursuing a major armed conflict with Iran to conclude that Iran threatens Iraqi stability or U.S. personnel located there and thus falls within the scope of the 2002 Iraq AUMF.

Indeed, the Trump administration may have already reached this conclusion. After all, the 2020 OLC opinion laying out the legal justification for the Soleimani strike—a heavily redacted version of which was secured via litigation in 2021—focuses on “Iran’s past and present activities in Iraq” (emphasis added), not just those of Soleimani himself or the IRGC Quds Force he headed. Elsewhere, OLC’s analysis similarly notes that the purpose of the strikes was to “deter Iran from conducting or supporting further attacks” and “degrade Iran’s and [Quds Force]-backed militias’ ability to conduct attacks, and end Iran’s strategic escalation of attacks on U.S. interests” (emphasis added). The implication is that the Trump administration determined that the legitimate target of the strike was not limited to Soleimani or the Quds Force, but extended more broadly to Iran itself. Focusing on Soleimani and his support for militias in Iraq helped provide the Iraq nexus required by the 2002 AUMF, but numerous other Iranian targets within Iraq—and maybe some outside Iraq, if they had a different nexus to the country—might well have done the same. The 2020 joint resolution that a majority of the House and Senate later adopted that cast aspersions on the idea that the 2002 Iraq AUMF authorizes the use of force against Iran may make this conclusion harder to reach today, but it is hard to know for certain.

Of course, Iran isn’t the only perceived threat that might trigger use of the 2002 AUMF. Since U.S. troops withdrew from Iraq in 2011, the country has also faced a major incursion by ISIL in 2014 and a brief-lived civil war with its autonomous Kurdish region in 2017, either of which could readily have been framed as a threat to Iraqi stability. So could many other more mundane, if still serious, threats to Iraq’s national security.

Some observers who continue to favor U.S. support for Iraqi security and stability—as the author does—may see some advantage in keeping the 2002 Iraq AUMF on the books in order to maintain maximum flexibility in crafting future U.S. policy. But this misreads the dynamics surrounding U.S. military intervention in Iraq. The U.S. occupation of Iraq remains highly controversial among Iraqis and continues to trigger widespread opposition to U.S. military activities there. While the U.S. military continues to play a central role in combating ISIL and provides other forms of security assistance at the Iraqi government’s request, these limited missions—neither of which rely on the 2002 Iraq AUMF for authorization—are all the Iraqi government seems willing and able to support.  When the Trump administration pursued a broader campaign of airstrikes against Iran-backed militias in 2019 and 2020 without the Iraqi government’s consent, the Iraqi parliament held a nonbinding vote to require a U.S. withdrawal. This in turn led the Iraqi government to pressure the Trump administration into negotiations to end the U.S. military presence there.

For the moment, the Biden administration appears to have satisfied these demands by symbolically ending the U.S. combat mission in Iraq in 2021, allowing other types of security cooperation to continue. But the most significant ongoing U.S. interests that require at least some military presence in Iraq—combating ISIL and strengthening the central government’s official security sector—are still at risk of being undermined by Iraqi perceptions of U.S. military overreach. Repealing the 2002 Iraq AUMF may make clear that the United States has no intention of reoccupying Iraq or pursuing broader activities there, outside of combating ISIL. And it may help reinforce that the other limited military actions the United States does continue to pursue—including self-defense strikes against Iran-backed militias—are necessary and proportional responses to that will end when Iran and its agents can no longer threaten U.S. personnel.

Arguments that repeal of the 2002 Iraq AUMF will embolden Iran are not persuasive, either. The 2002 Iraq AUMF has not prevented Iran from acting provocatively in Iraq for the past 20 years, and it is unlikely to do so in the future. If anything, Iran often seeks to provoke the United States into military responses that it knows will undermine popular Iraqi support for U.S. cooperation. Repeal will weaken the narrative of American imposition that Iran often seeks to cultivate and reinforce through such provocations. By taking away a seeming blanket authorization to act against Iran for ambiguous activities in Iraq, repeal may also help make clear that the executive branch sees its ability to act militarily against Iran as correlating more strictly with the extent to which Iranian agents threaten U.S. personnel, providing a more directly linked incentive to refrain from such provocations. And if nothing else, repeal also provides assurances that, if the United States does at some point decide that broader military action against Iran is warranted, the executive branch will pursue it with Congress’s express and specific support, not on such weak and controversial grounds as an antiquated authorization for a different war that ended more than a decade ago.

For better or worse, the trajectory of modern war powers has been towards greater executive branch authority. Self-aggrandizement by the executive branch has played a central role in this evolution, but so have congressional acquiescence and judicial abdication. The last clear redoubt of Congress’s constitutional authority is over major wars, which even the executive branch acknowledges as requiring affirmative congressional consent under the Constitution. The 2002 Iraq AUMF in turn serves as a significant—and dangerous—carveout from this reservoir of authority. Through it, the executive branch views Congress as—effectively, if not intentionally—having provided its advance authorization to nearly any sort of armed conflict with a nexus to Iraq, a country cursed with a wide array of challenges, including a troubled relationship with a major U.S. rival. Political considerations have thus far discouraged recent presidents from relying solely on the 2002 Iraq AUMF for military action, to the point that its repeal would not compromise any ongoing military operations. But in weighing repeal, Congress must ask itself how confident it is that this will remain true moving forward—and how much of its own remaining authority over war and peace it is willing to wager. 


The experience of the 2002 Iraq AUMF offers Congress many lessons about authorizing the use of military force. Open-ended and deferential language of the type used in the 2002 Iraq AUMF invites broad interpretations by the executive branch, in ways that Congress might not anticipate or intend. When Congress then appropriates funds for or enacts legislation relating to activities that rely on these broad interpretations, this may well be seen as implicitly ratifying those interpretations, even if this is not what Congress intends. And no federal court seems likely to step in and limit these interpretations unless Congress makes its institutional disagreement clear. But Congress may be able to set clearer limits by using narrower and more specific authorizing language when drafting AUMFs, making clear that appropriations and other framework legislation does not authorize activities not authorized elsewhere, and building sunsets into AUMFs that require periodic congressional review and reauthorization, among other measures.

But such proposals come too late for the 2002 Iraq AUMF. The diverse ways in which the executive branch has used the 2002 AUMF over the past 20 years—and Congress’s interactions with them—have already left a historical gloss that dramatically expands its meaning in the eyes of the executive branch that interprets and applies it. This view has been reiterated across presidential administrations of both political parties, underscoring its durability. Nor do the federal courts seem inclined to constrain it, unless Congress does something to change the statutory status quo on which it is based.

Repeal is the most straightforward way for Congress to do this.  A bipartisan majority of Congress has already voted once to limit military action against Iran under the 2002 Iraq AUMF, and assessments of votes in the current 117th Congress suggest that the Senate repeal proposal—which has been approved by the Senate Foreign Relations Committee but has not received a floor vote like its companion legislation in the House—would have enough votes to pass, even over a potential filibuster. The only question is whether repeal can be incorporated into one of the remaining pieces of end-of-year omnibus legislation, or will be seen as warranting some of the limited floor time that this Congress has left to advance its remaining legislative agenda. Either way, what hangs in the balance is not a mere act of administrative housekeeping, but a dangerous exception to one of the few areas where Congress still has primary authority over matters of war and peace.

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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