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On June 17, the House of Representatives voted in favor of a resolution introduced by Rep. Barbara Lee to repeal the 2002 Authorization for Use of Military Force (AUMF) against Iraq. A similar measure is expected to pass in the Senate and to be signed by President Biden. Lee argued that “this authorization no longer serves any operational purpose. As long as it remains on the books, the law is susceptible to further abuse by any President.” The pending—and likely to succeed—Senate version of the resolution additionally repeals the 1991 AUMF passed shortly before Operation Desert Storm began. Senate Majority Leader Chuck Schumer echoed Lee in arguing that the repeal would eliminate the possibility of a future administration “reaching back into the legal dustbin to use it as a justification for military adventurism.” A group of Republican senators, however, has threatened to derail the rescission of the force authorization, worrying specifically about how such a repeal would be perceived by U.S. partners, as well as adversaries such as “ISIS and Iranian backed militia groups.”
The question, though, remains what effect such a repeal would have. The Biden administration states that the U.S. “has no ongoing military activities that rely solely on the 2002 AUMF as a domestic legal basis” and that its repeal “would likely have minimal impact on current military operations.” The legal framework for the use of force absent congressional authorization is so malleable that—in the words of Jack Goldsmith and Curtis Bradley—it “provides no meaningful constraint on presidential power.” Thus, it is not clear that repealing an authorization the executive branch views as being superfluous will have any real effect. Instead, there is the possibility that the White House will continue acting no differently than if the AUMF(s) remained on the books, and there is ample reason to suspect this might be the case. As John Bellinger noted for Lawfare in February, Biden justified a strike in Syria not via either the 2001 or 2002 AUMF, as previous presidents had done, but instead “pursuant to my constitutional authority to conduct United States foreign relations and as Commander in Chief and Chief Executive”—in other words, based on Article II powers alone. Likewise, strikes in Syria and Iraq in late June were justified similarly. In the end, it is unlikely that there will be any substantial change in behavior compared to recent years even after a repeal because the additional political power the 2002 AUMF gave the presidency already dissipated long ago. Thus, repealing what is effectively a dead letter will do little to change actual use-of-force behavior.
The Political Function of Formal Authorization
Formal congressional authorization for the use of military force is often viewed through a legal lens, but AUMFs also serve as important political instruments. This is most obviously manifested when presidents disclaim any legal need to acquire authorization while simultaneously seeking such approval (clear examples being Johnson in 1964, George H.W. Bush in 1991, George W. Bush in 2002 and Obama in 2013), and it is widely recognized that political expediency is the real driver of such behavior. Nonetheless, it would be a mistake to dismiss these as “merely” or “just” political considerations, as such a characterization misleadingly depreciates how important such approval can be in White House decision-making. A “mere” lack of congressional authorization stopped Eisenhower from intervening in Indochina in 1954, prevented Johnson from using force in the Middle East in 1967 and against North Korea in 1968, and deterred Ford from evacuating more Vietnamese nationals as Saigon fell in 1975. More recently, even after asserting that he had already decided to use force and that his Article II authority was sufficient for such an endeavor, Obama “blinked” in the Syrian chemical weapons crisis in 2013 when given the opportunity to enforce his “redline” absent congressional backing.
These historical cases elucidate a particular political concern of administrations since the beginning of the Cold War: an anticipation of being severely punished politically by Congress if a large, unauthorized use of force were to end poorly. Presidents can, however, substantially mitigate this ex post downside risk if they get Congress “on the record” in support of a use of force ex ante. While it is already well recognized that presidents are willing to undertake smaller uses of force unilaterally—for example, airstrikes similar to those ordered by Biden—there is little evidence they are willing (regardless of what they claim in mere rhetoric) to undertake substantial uses of force without clear congressional backing. Of course, this dichotomy—a willingness to act unilaterally in small scale uses of force, but deploying force on a larger scale only when congressional backing is secured—is consistent with the “anticipated nature, scope and duration” test utilized by the Office of Legal Counsel over recent decades. Due to the overwhelming use of historical practice in creating this legal test, however, it seems likely the “law” has developed as a consequence of observed political behavior rather than vice versa (that is, behavior being significantly altered by a legal standard already recognized as highly malleable).
Such political cover, however, is not everlasting. While a law may stay relevant from a legal perspective so long as it remains on the books, from a political perspective an AUMF decays just as rapidly as its perceived legitimacy diminishes. Because the primary function of an AUMF is to prevent a defection of congressional support for a war over time, once Congress has turned against American involvement in a conflict, the formal force authorization itself has ceased to be of any real value. Applying this line of reasoning to the question of “zombie” AUMFs, such behavior over the past seven decades suggests three things. First, those large-scale uses of force that tend to be undertaken only with congressional support are unlikely to be initiated under the guise of an outdated AUMF. A zombie force authorization simply would not fulfill the White House’s perceived political need to get Congress committed to a conflict ex ante, because attempting to justify a major use of force based on an old AUMF would likely do little to prevent congressional attacks (indeed, it might even encourage them). Thus, it would fail to serve the political function that presidents seek from AUMFs in the first place. Second, small-scale uses of force will continue regardless of whether formal congressional authorization—be it new or antiquated—seemingly covers an action. A simple Article II justification can always be used, and presidents have never been shy about doing so for more minor military action. Third, these first two points together suggest that repealing antiquated AUMFs is unlikely to significantly alter use-of-force decisions in the future (illustrated in Figure 1).
Figure 1. The impact of antiquated AUMFs and their repeal on willingness to use force.
The Last Repeal: The Gulf of Tonkin Resolution
The Biden team’s convenient switch in legal theory away from AUMF(s) is reminiscent of the last time a high-profile force authorization was faced with imminent repeal—the Gulf of Tonkin Resolution nearly 50 years ago. The immediate motivation for the repeal of the resolution was President Nixon’s decision to advance into Cambodia with U.S. ground forces in the spring of 1970, and the administration had, indeed, originally justified the intervention under the congressional resolution. But only a week later—after congressional threats to repeal the resolution began gaining credibility—the administration simply, like the Biden White House in February, switched the legal theory it relied on and instead emphasized the president’s Article II powers. Indeed, the Vietnam War would continue with substantial U.S. involvement for more than two years after the repeal, and the legal revocation of the 1964 resolution thus seemed to matter little. Yet, where legal constraints fail, political constraints can remain quite robust, and it is these substantial political constraints that were beginning to have an effect long before the resolution was repealed.
At the onset of the Vietnam War, the Johnson administration, like most other postwar presidencies, publicly declared it did not need congressional approval and yet simultaneously privately realized that such formal authorization would be a necessary political precondition for substantial combat operations. Johnson sought a formal vote for the war in order to “keep those 502 Congressmen right chained to me all the time with that resolution.” One of the few members of Congress who declined to vote in favor of the resolution likewise stated that the administration sought such a vote of support in order to “seal the lips of Congress against future criticism.” For several years, Congress accordingly kept up its support for the war despite successive major escalations in American involvement and fatalities. After the fierce and unexpected Tet Offensive in early 1968, however, Congress began voicing its disapproval of the war and Johnson chose to deny further troop escalations sought by the Pentagon once he recognized that members of Congress had turned against the war. According to George H.W. Bush, it was then that Johnson realized members of Congress who previously remained “chained” to the war via their vote for the resolution had finally “painted their asses white and ran with the antelopes.”
Likewise, while the Nixon administration publicly attempted to convey steadfast resolve against vocal congressional criticism during the Cambodian incursion in 1970, in private the president pushed for more and more curtailments of U.S. operations in the nation after realizing he had severely underestimated the congressional backlash his action would provoke. Indeed, the White House cut back the operation so aggressively as to effectively defeat much of the main purpose of the incursion’s launch in the first place. Despite the resolution still being on the books, Congress’s growing opposition to the war was having a major effect on how the executive chose to prosecute the conflict.
In truth, the nature of the war for the U.S. changed substantially—both before and after the repeal—as the Nixon administration sought to minimize U.S. casualties. Plotted in Figure 2 are U.S. combat fatalities by date, with the two vertical red dashed lines marking the passage and later repeal of the Gulf of Tonkin Resolution. Fatalities in teal represent those during the period of formal authorization, while fatalities in orange are those that fall outside the time period. As the plot demonstrates, the vast majority of American combat fatalities in the war occurred while the authorization was still valid law, but fatalities had been decreasing long before the formal revocation of congressional authority. Congressional pressure manifested through other means—speeches, hearings and the introduction of anti-war legislation—had compelled the executive to order massive troop withdrawals years before the actual repeal.
Figure 2. U.S. combat fatalities in relation to the passage and repeal of the Gulf of Tonkin Resolution (indicated by the two vertical red dashed lines).
Precisely because the primary function of ex ante congressional approval is to prevent ex post attacks on the president, once Congress has shown itself willing to oppose the war, the authorization had ceased to be of any real value. In this sense, formal repeal in 1971 was analogous to removing the stable door long after the horse had already bolted. Notably, while enormous value had been placed on the resolution at the beginning of the war, nary a mention of the potential impact of its repeal is found in the White House’s private decision-making at the time of its repeal. This is unlikely to be explained by a simple lack of concern for congressional sentiment at the time—in Kissinger’s recollection of the time period, concerns about possible congressional actions seemingly dominated White House decision-making—but rather because the Gulf of Tonkin Resolution specifically had already become worthless politically.
Although the U.S. remained engaged in the war for four years after Tet, this was made possible by Nixon’s Vietnamization program that helped maintain public support for (significantly deescalating) American involvement. Notably, Nixon had far higher approval ratings for his handling of the war than Johnson had experienced—Johnson declined to run for reelection in 1968 primarily because of the war, whereas Nixon won reelection in 1972 in a landslide. Indeed, the Nixon administration transformed American involvement in the war from one of ground forces to one of primarily air power, despite the fact he was not simply trying to “cut and run” from the conflict but actively sought “peace with honor” in Vietnam (compare this to his 1972 opponent in the presidential election, George McGovern, who declared, “Come Home, America!”). Figure 3 illustrates both U.S. fatalities over time and the amount of ordnance U.S. aircrafts dropped in Southeast Asia. Casualties had been decreasing since 1968—well before the repeal of the resolution—and continued to decrease substantially thereafter. U.S. bombing, in contrast, accelerated greatly after 1968 and did not peak until 1972. Thus, while the war dragged on long after the repeal, the war for the U.S. in 1972 was of a far different nature than the war in 1968.
Figure 3. U.S. fatalities (dark gray) and ordnance dropped (red line) in relation to the passage and repeal of the Gulf of Tonkin Resolution (indicated by the two vertical blue dashed lines).
Even so, this strategy also had limits. Nixon himself admitted in private that it would be politically impossible to reintroduce American air support over Vietnam—to say nothing of ground troops—after the last American prisoners of war were returned by North Vietnam in 1973. Notably, the Ford administration declined to intervene in 1975 after North Vietnam clearly violated the 1973 peace agreements, and it even declined to undertake a more substantial effort to evacuate South Vietnamese particularly endangered by the communist advance. Thus, once American involvement in Vietnam ended in 1973, reengagement proved politically impossible for presidents.
The lesson here is that the substantial political power an AUMF grants the president dissipates not with legal repeal but, rather, once Congress no longer feels politically bound by its prior vote. In the current debate over the 2002 AUMF, such power clearly dissipated well over a decade ago. While presidents in recent years have occasionally cited the 2002 AUMF for authority, this is likely simply window dressing for action that would have been undertaken regardless. In a hypothetical world in which the 2002 AUMF was repealed in, say, 2011, would President Obama have conducted the counter-Islamic State campaign differently? This is highly unlikely—as Tess Bridgeman and Ryan Goodman point out for Just Security, the Obama administration was actively seeking the repeal of the 2002 AUMF just as it was conducting the campaign. Would President Trump have been deterred from conducting a strike against Iranian Maj. Gen. Qasem Soleimani due to a minor legal technicality? The answer is likely a self-evident no. These actions would have been undertaken even without the AUMF, and they were well within the scale of operations that other presidents have been comfortable undertaking unilaterally.
The presence or absence of an AUMF is going to affect presidential behavior only when it comes to the contemplation of major use of force, but in the “full-scale” war context, the 2002 AUMF is as dead as Saddam Hussein. Only a handful of legislators still in Congress might even theoretically feel personally bound by their prior vote in 2002, and thus it is precisely because “the vast majority of those serving in Congress has never voted to authorize a military operation” that these antiquated AUMFs on the books have virtually zero political utility. Consequently, for these larger uses of force, the repeal of the Iraq AUMF(s) will likewise do little to change the behavior we observe.
The Question of Utilizing an Antiquated AUMF: The Iraq War
The simple political reality is that a president is not going to start a major war by relying on an antiquated AUMF—repealed or not. Indeed, the best proof of this is the 2002 Iraq AUMF itself. Like nearly all other administrations after World War II, the George W. Bush administration publicly maintained it did not constitutionally require congressional authorization to invade Iraq in the early 2000s. From a purely legal perspective, the administration had a much stronger case for war than other presidents had had in past crises. While Truman, Johnson and George H.W. Bush would have had to rely solely on their Article II presidential powers had they entered their respective wars unilaterally (only Truman actually did so—though, with very strong congressional support), George W. Bush had multiple existing statutes to plausibly point to for authority.
First—and most importantly—there was the 1991 AUMF from the Gulf War that was still binding law. Second, there was the more recent 1998 Iraq Liberation Act, which declared that “it should be the policy of the United States to seek to remove the Saddam Hussein regime from power in Iraq and to replace it with a democratic government.” Lastly, there was even an attempt by the administration to claim that the 2001 AUMF—authorizing the use of force against the perpetrators of the 9/11 attacks—was also a source of authority. A legal memorandum written by the Office of Legal Counsel—in part, citing the Korea precedent—even averred that the president had the power to use military force to conduct regime change in Iraq solely based on his inherent Article II powers. Unsurprisingly, the White House counsel also found the president had all the authority necessary, arguing that “the authority to invade Iraq rests on three legs: the 1991 resolution endorsing the Persian Gulf war, a Congressional resolution enacted just after the Sept. 11 attacks and the president's role as commander in chief.”
There was also substantial precedent of using military force against Iraq under the 1991 resolution in the decade after the Gulf War. No-fly zones in the southern and northern parts of Iraq had been maintained by the U.S., the U.K. and France since the 1991 cease-fire, and President Clinton had ordered direct strikes in 1993, 1996 and 1998. Public opinion, furthermore, was already in favor of the use of force against Iraq by the summer of 2002.
Nonetheless, despite all the possible legal avenues the administration had—a thought even more striking when one considers the willingness of the same administration to exercise aggressive presidential powers in other national security contexts—there is little indication that major action would have been undertaken had renewed congressional authorization not been secured. Karl Rove reports that there was indeed a robust debate in the administration over whether Congress needed to be approached for renewed approval, with Vice President Cheney and some of his aides arguing that the president should avoid it. Nonetheless, by the end of August 2002, “a consensus had been reached among Mr. Bush’s advisers” that congressional approval needed to be sought. While Bush saw that it was not strictly legally necessary, he nonetheless thought the country—and his own position—would be “better served by a broader range of support.” Bush’s assistant for legislative affairs, Nicholas Calio, later stated: “We were going to pursue a resolution because the President felt … if this was going to happen there needed to be a vote.”
The White House was under no illusions about the severe political risks it would be taking by acting alone. As the New York Times reported at the time:
Despite confident assertions by the White House this week that the president has all the legal authority and Congressional approval he needs for an invasion of Iraq, [administration] officials said there was in fact widespread recognition that it would be unwise to attack without a new expression of support from Congress.
And most relevant to contemporary concerns of a president utilizing the old AUMF(s) today, in 2002 it was pressure from Congress itself that deterred unilateral presidential action:
Many lawmakers have lined up to denounce the administration for asserting that the 1991 resolution authorizing the Persian Gulf war provides a legal justification for a new invasion. One official said that while there may be a by-the-book legal argument, “it’s very hard to get away with it in a political sense.”
Notably, in the international law context, the administration did prove willing to utilize an antiquated authorization, as the underlying use of force authorization was U.N. Security Council Resolution 678 from the Gulf War. But in the domestic context it was tellingly not willing to analogously rely on the 1991 AUMF. The Clinton administration had been willing to rely on the Gulf War AUMF for its actions throughout the 1990s, but these actions were all much smaller than the 2003 invasion and were well supported by Congress. Likewise, the Islamic State campaign begun under President Obama was partially justified under the 2002 AUMF, but—again—this campaign was widely supported by successive Congresses and yielded far less than 1 percent of the American casualties suffered in the Iraq War. There is simply no serious precedent of a president bringing a zombie AUMF back from the dead to start a substantial use of force contrary to the wishes of Congress.
Some observers might point to the 2020 Soleimani strike as a counterexample—indeed this event seems to have been a major catalyst for the current repeal in the first place. While there was unanimous recognition that Soleimani himself was a committed and dangerous enemy of the United States, there was a worry that his killing would lead to a larger conflict with Iran. But, contrary to many worries, the events themselves show the administration was fully unwilling to escalate the conflict. Indeed, in retaliation for the death of Soleimani, Iran conducted a ballistic missile attack against bases in Iraq that housed U.S. forces. Yet, upon learning that many U.S. soldiers had been injured in the strikes, the administration affirmatively chose not to further escalate the situation as it easily could have. Instead, it intentionally withheld the information and publicly emphasized that no Americans were killed in the Iranian strike. When the injuries were later made public, Trump infamously dismissed them as mere “headaches.” Thus, when looking at actual actions—and not just threats and posturing—there is little evidence of presidents willing to commence serious conflict based on an antiquated AUMF.
Because AUMFs fundamentally serve a political, and not simply legal, purpose, once that political value has ended, they’re effectively dead letters. In the case of the 2002 AUMF, Saddam is long dead and the Iraq War is long over. The political benefits a president secures by acquiring formal congressional authorization—most importantly boosting public opinion in the short term and securing congressional backing over the longer term—would simply not apply if a president were to attempt to justify a significant use of force opposed by Congress via a zombie AUMF. Thus, without the benefits an AUMF entails, there is little reason to suspect presidential behavior under an antiquated AUMF would be significantly different than what we might observe when operating under no AUMF at all.
But even if repealing the AUMF(s) is unlikely to alter presidential behavior in any significant way, there’s also little reason not to repeal the legislation. In fact, if it were the case that the White House’s use-of-force calculus were unchanged by a repeal, this would seemingly fully assuage the problem that Sens. Marco Rubio, Mitt Romney and others have raised in possibly losing deterrent credibility against “ISIS and Iranian backed militia groups.” Because recent presidents of both parties have clearly demonstrated a willingness to strike groups such as these without formal congressional approval, there is little reason to suspect striking a superfluous law from the books will call American credibility into question. In contrast to coercive threats against strong nation-states (such as against China over Taiwan or against a Russian-backed Syria) in which there would be a serious question of whether a president would respond absent formal backing from the legislature, no one seriously entertains doubts over whether a president would strike a relatively weak terrorist group.
Furthermore, from a constitutional hygiene perspective, it is discomforting to see decades-old force authorizations remain valid law. As Matthew Waxman has pointed out, there is even a 1957 AUMF on the books that is just now becoming the focus of possible repeal as well. For these reasons, the repeal of the Iraq AUMF(s) should not be dismissed as an undeserving endeavor—a proactive Congress interested in overseeing military conflict should be applauded. Just don’t expect this action alone to do much to change the presidential behavior that has taken place in recent years.