Congress is once again renewing efforts to replace the outdated and overstretched 2001 Authorization for Use of Military Force (AUMF) and repeal thezombie2002 AUMF. These are important and overdue tasks, which should be welcomed by the Biden administration, given its long-stated support for replacing the 2001 AUMF with “a narrow and specific framework” tailored to today’s “terrorist threats.” As with prior attempts by lawmakers to take back some measure of control in this arena, determining the scope and limitations of a new AUMF – assuming one is needed at all – presents policy and political challenges. But lessons from the more than two decades since Congress last authorized war could point towards emerging bipartisan consensus on at least a few key parameters: any new AUMF should clearly name the enemy against whom force is authorized; and it must have a reauthorization requirement (or sunset) to ensure future Congresses periodically vote on whether the country should still be at war.

There is a third necessary corrective to the status quo that risks slipping under the radar: Any new AUMF must be limited to only the clearly specified non-state armed groups Congress has voted to authorize war against. Specifically, it must make clear that the authority it confers on the President to wage war does not extend to unnamed “associated,” “successor,” “affiliated,” or other forces against whom Congress hasn’t voted to use force. To do otherwise risks hard-wiring a multi-front war that can continue to expand by unilateral presidential action – without Congress fulfilling its constitutional duty to decide when and against whom the nation should be at war.

How We Got Here: The “Associated Forces” Innovation

The 2001 AUMF is widely understood to authorize force against al-Qa’ida, which “committed” the 9/11 attacks, and the Taliban, which “harbored” al-Qaida in Afghanistan at the time. But in the 22 years since 9/11, the United States’ counterterrorism wars have expanded to encompass new enemies not contemplated in the 2001 AUMF. The most important legal move that enabled this expansion was the creation of the concept of “associated forces.” Rebecca Ingber explained the term in her Just Security article Legally Sliding into War:

[“Associated forces” is] a term the executive branch crafted to identify groups that are connected to al Qaeda and meet relatively loose criteria. By relying on this concept and suggesting (through terms like “co-belligerency”) that it has some clear limiting principle derived from international law (it does not), the executive branch has successfully asserted that its domestic statutory authority to use force extends beyond the core groups referenced in the 2001 AUMF…

Without any clear content behind the concept of “co-belligerency” in existing law, the Obama administration advanced its own standard to conclude whether an armed group constitutes an “associated force” covered by the 2001 AUMF: “First, the entity must be an organized, armed group that has entered the fight alongside al-Qa’ida or the Taliban. Second, the group must be a co-belligerent with al-Qa’ida or the Taliban in hostilities against the United States or its coalition partners.” 

There is no particular law the Executive branch cites, international or domestic, from which this test can be ascertained, but it has become durable nonetheless. The Trump administration relied on this same test in habeas litigation (Doe v. Mattis), and the Biden administration has not deviated from this approach. Congress (and lower courts) have accepted the overall concept of associated forces in detention-related contexts, but neither branch has weighed in on the Executive’s specific determinations, or the standard it applies in making them. 

While the list of groups the Executive believes to be covered by the 2001 AUMF is unfortunately currently classified, to date, this standard has been publicly deemed by the Executive branch, without congressional or judicial imprimatur for any individual determination, to apply not just to groups that were operating in roughly the same theater as al-Qaida and the Taliban in Afghanistan, like the Haqqani Network, but also groups such as al-Qaida in the Arabian Peninsula (AQAP), operating in Yemen, al-Shabaab in Somalia, certain individuals who are part of al-Qa’ida in Libya,” “certain other terrorist or insurgent groups affiliated with al-Qa’ida or the Taliban in Afghanistan,” and al-Qaida in Syria.

The Pandora’s Box of “Successor Forces”

A second innovation of the Obama administration extended beyond the concept of “associated forces” to bring “successor forces” within the claimed scope of the 2001 AUMF. This second novel theory was adopted in order to bring ISIS within the 2001 AUMF’s scope as it was sweeping across Syria and Iraq, following about six weeks of strikes by the Obama administration against ISIS targets justified under the President’s Art. II authority. At the time, ISIS was in open hostilities with the 2001 AUMF’s true target, al-Qa’ida, which rendered it distinctly outside the two-prong definition of “associated forces” articulated by the administration. Instead, the Executive branch adopted the theory that ISIS fell under the 2001 AUMF as a “successor force” to al-Qa’ida, sometimes labeling the two organizations as “one and the same” despite their open split years prior. 

Nine years on, without sustained pushback from Congress, the theory raises fewer eyebrows, but it’s worth recalling what a departure it was as a legal move in 2014. As Bobby Chesney wrote at Lawfare when the news of this interpretive move first broke:

I’m astonished to learn this evening that the Obama administration, having previously justified 140+ airstrikes against IS[IS] in Iraq on Article II grounds alone (at least insofar as the stream of WPR reports indicated), has discovered that IS all along was covered by an AUMF…and not the 2002 AUMF relating to Iraq, but the 2001 AUMF relating to al Qaeda.

To be sure, there was a time when this would have been a perfectly fine argument; IS is the descendant of AQI [al Qaeda in Iraq], after all, and for many years it would be easy to show that AQI was an associated force of AQ engaged in hostilities against the US. But so far as I know no one seriously denies that it has since had a fundamental rupture with AQ, and indeed engages in combat at times with AQ’s Syrian outfit, the al Nusrah Front. For the administration to claim, as Marty Lederman reports here, that IS nonetheless remains subject to the 2001 AUMF both because of this past and because IS though now independent in some fashion claims to be the “true inheritor” of “bin Laden’s legacy” (and because AQAP and other AQ associated forces have made ambiguous statements, for whatever reason, applauding IS’s claims and achievements) is just stunning from a legal perspective.

What may be even more stunning almost a decade later is that no limiting principle has yet been articulated for this approach to determining who Congress authorized war against back in 2001. There’s nothing to say, for example, that the “associated force” of a “successor force,” for example, is not covered by the 2001 AUMF. (The Doe v. Mattis habeas case concerning an American citizen held by the U.S. military in Iraq as an ISIS detainee could have brought this issue to a head, but was resolved before the case reached the merits when the detainee was released from U.S. custody.)

Conflict-Creep is the New Normal

Rebecca Ingber has succinctly summarized the upshot of this state of affairs:

This position [on “associated” and “successor” forces] means that the executive branch, through its own legal interpretation of a 20-year-old authorization—a statute that was intended to sanction an immediate response to the 9/11 attacks—and its application of that legal theory to facts it alone may access, may continuously update its authority to use force against new groups without going back to Congress. … The result is that the president holds the unilateral power to extend the war to groups that many Americans do not know exist.

It should not be terribly surprising that some in the Executive branch would prefer that the President retain this implied power in any new AUMF, while some in Congress, particularly those who seek to reassert Article I control over authorizing war, have vocally opposed it. As Sen. Rand Paul (R-KY) wrote in 2018 in response to a draft replacement AUMF that would have blessed the President’s ability to add new “associated forces” to its scope without a prior vote in Congress:

That isn’t an AUMF. That isn’t Congress reclaiming its constitutional duties. That’s a complete rewriting of the role of the executive and of the constitutional separation of powers. […] 

If this AUMF is passed, Congress will have chosen to make itself irrelevant on the issue of war. Currently, use of force without congressional authority is limited by the War Powers Act to national emergency or imminent attack. No more, under this AUMF. […]

Handing war-making power from Congress to the executive branch is not an exercise in congressional power. It is the final and full abandonment of that power. It is wrong, it is unconstitutional, and it should be stopped.

In a hearing on that same draft AUMF (known as the “Corker-Kaine AUMF”), Senators on both sides of the aisle and the two Republican witnesses expressed grave concerns about the embrace of presidential authority to add new “associated forces” to the authorization. Here’s a quick round-up of those statements:

Senator Mike Lee (R-UT) called the current state of affairs, where the executive branch has unilaterally expanded the scope of AUMFs, “scary,” and Senator Bernie Sanders (I-VT) warned that the consequences of Congress neglecting its constitutional duty were “dire and horrific” for both America and the rest of the world.

One of the witnesses, Professor Jonathan Turley, agreed with Senator Paul’s assessment, stating that the existing AUMFs and the proposed Corker-Kaine [AUMF] “put war-making on autopilot.” Another witness, Fox News legal contributor Judge Andrew Napolitano, concurred, calling the proposed Corker-Kaine AUMF “profoundly unconstitutional.” Napolitano argued that the proposal would cede to the executive branch Congress’s constitutional duty to declare war by requiring a Congressional supermajority—a veto-proof two-thirds of both the House and Senate—to stop the president from unilaterally expanding the war to new groups and new countries. Napolitano went on to criticize both the existing AUMFs and the proposed Corker-Kaine replacement as “putting a loaded gun in the desk drawer of the president, ready for him to take it out and shoot it whenever he wants.”

Rather than go down this path again, if Congress wants to protect against the expansion of war to new groups without its authorization, what can it do?

How Any New AUMF Should Limit Conflict-Creep

As Ryan Goodman, Stephen Pomper, Steve Vladeck and I wrote in 2021 when we put forward seven principles for any new AUMF that aims to replace the 2001 statute, it is imperative to “explicitly preclude use of force against countries or organized armed groups other than those specifically named.” Specifically: 

Any new AUMF must be clear that force is not authorized against any nations, armed groups, or individuals other than those explicitly named in the statute, including any purported “associated forces,” “successor forces,” “co-belligerents,” “affiliates,” “splinter” groups, or other “related” groups or nations. (If an identified  group merely changes its name but remains otherwise the same group, it would continue to be covered.) This would also be intended to prevent a conflict from spilling into new regions or countries where related groups operate, absent explicit congressional authorization. 

Crucially, there should be no expedited procedures for expanding the authorization over time. Congress should affirmatively vote – using normal procedures – to authorize new armed conflicts or expand existing ones.

Brian Finucane and Steve Pomper similarly concluded in 2021 that any revised AUMF “should remove the capacity of the executive branch to change the scope of the war by adding new ‘associated forces’ without first obtaining congressional permission…”

A draft 2001 replacement AUMF offered by Rep. Gregory Meeks (D-NY) (ranking member of the House Foreign Affairs Committee) and others earlier this year, among other important provisions, did just that. It explicitly stated that the authority it conferred to wage war “shall not apply to an entity” not named in the operative section of the statute, “whether or not the entity is… an affiliate, associated force, or successor entity of an entity” named in the AUMF, or whether it is “involved in an armed conflict against a force of a United States ally or partner.”

But What if a Terrorist Group We’re at War with Changes its Name?

Some have argued that without the ability to expand a war to “associated forces,” groups like al-Qa’ida or ISIS will simply change their names to escape from coverage under domestic U.S. authorizations for use of force. To be clear, this is usually not the context in which the “associated” or “successor” forces tests have been used to date – they have instead been applied to new groups that have “entered the fray,” not existing groups that change their name after reading the U.S. Code. (And under the current 2001 AUMF, with respect to a true name change situation, the Executive branch would be on solid ground arguing that it remained covered given that the AUMF doesn’t use any names at all – even al-Qaida and the Taliban are not explicitly named in the statute, but rather described by reference to the acts they committed with respect to the 9/11 attacks, so the name of the group is less relevant.) 

But say a group with which the United States was at war did change its name, and the AUMF authorizing force against it contained the limitation described above? There’s an easy fix to that potential issue, which the Meeks AUMF also addressed by providing that the authority to use force “may not be construed to cease to apply” to a group that “adopts a different name” (it also required a presidential determination about any such group be provided to Congress within 60 days of determining a name change had occurred).

Reasserting Control Means Taking Votes

Beyond name changes, it remains possible that a new, organized armed group might become engaged in a series of hostilities with U.S. armed forces, or present an imminent threat of a serious armed attack against the United States. It is also possible that such a group has a relationship of some sort – whether closely connected operationally or not, whether with shared history or not – with a group like al-Qaida or ISIS. What should be done in such a situation? 

To begin with, it bears noting that the President retains the authority under Art. II of the Constitution to respond to an imminent threat of armed attack, absent prior congressional authorization, including in situations concerning an imminent threat to U.S. nationals abroad. President Biden, like those before him, has used this Art. II authority to do just that on at least four occasions, according to the reports he has provided to Congress pursuant to the War Powers Resolution.

And if a President considers that the United States is commencing, or should commence, a sustained war with a group against which force is not already authorized by Congress, he or she should make the case to Congress and Congress should put it to a vote. That is the system laid out in the Constitution, and it was a feature, not a bug, to include this among the powers of the slower-moving political branch as a check against excessive or unpopular war-making. With the judiciary having essentially bowed out of the merits on most cases involving the authority to use force for the past several decades, it remains the only check we have. 

With two decades of hind-sight, it should now be clear that “an armed conflict that has steadily expanded over three continents and is now two decades old, is an aberration in the history of the United States.” Putting the notion of “associated forces” to rest in any new AUMF is a key part of getting the political branches on a more accountable, and ultimately stronger, path ahead. 

IMAGE:  The U.S. Capitol stands on January 13, 2021 in Washington, DC. (Photo by Stefani Reynolds/Getty Images)