Editor’s note: This article is the fourth installment in our Still at War Symposium, which can be accessed here

Even as Russia’s invasion of Ukraine has rightly captured the world’s attention and significant global resources, it is important to remember that the fallout from the U.S.-led war in Afghanistan continues. The Taliban takeover, following the chaotic withdrawal of U.S and international forces in August 2021, has spawned enormous refugee outflows and the potential for the resurgence of multiple terrorist groups within the country. The Taliban regime has significantly infringed on the rights of women and girls, and sanctions against the regime for its human rights abuses, on top of the toll of decades of war, have contributed to a burgeoning humanitarian catastrophe. The U.S. legal posture towards Afghanistan, therefore, holds ongoing significance. Specifically, we need to ask the question: Does the United States still consider itself to be waging a forever war against terrorist groups in Afghanistan?

The answer so far appears to be yes, even though U.S. President Biden proclaimed that, with the withdrawal of U.S. armed forces from the territory, “the United States ended 20 years of war in Afghanistan — the longest war in American history.” But while fighting against the Taliban may be over (at least for now), Biden has also signaled that the United States will rely on  “over-the-horizon” capabilities to continue the war against terrorist groups in Afghanistan. Indeed, it seems the Biden administration decidedly has not declared the end of the forever war legal paradigm. To the contrary, the U.S. government continues to take the position that it is engaged in a broad, ongoing, transnational armed conflict against al-Qaeda and terrorist groups, including in Afghanistan, and that the dominant international legal framework governing extraterritorial operations against these groups therefore is the law of war, also known as international humanitarian law (IHL).

Why does it matter whether or not we are formally still at war? It is, after all, true that IHL imposes important rules that protect civilians and limit the conduct of actors within armed conflict. But significantly, these rules are different from—and often much more permissive than—other rules of international law that might govern the use of force and detention in extraterritorial counterterrorism operations outside of war. The jus ad bellum is a key body of international law that regulates the extraterritorial use of armed force and would govern decisions to strike terrorist groups in Afghanistan. Likewise, international human rights law (IHRL) imposes strong protections for the right to life, including a prohibition on the pre-planned use of lethal force against specific individuals, as well as protections for those who might be detained or tried, such as rights to be free from arbitrary arrest and due process. If the United States is no longer at war in Afghanistan as a matter of law, then IHL should not apply, and IHRL and jus ad bellum frameworks become even more relevant. 

Many other states and international actors take a narrower view of the scope of IHL as a matter of law and embrace a correspondingly broader role for IHRL (and the jus ad bellum) with respect to extraterritorial counterterrorism operations. Given that Biden and other senior administration officials have vowed to support human rights around the globe, one might think this stance should include a commitment to abandon the war paradigm and expand the human rights paradigm as a matter of law and not just rhetoric. The exit of U.S. armed forces from Afghanistan, therefore, leaves open the question: Will the Biden administration go beyond current statements and explicitly articulate a reduced scope for the war paradigm for extraterritorial counterterrorism operations in Afghanistan as a matter of international law? 

The new military posture for the United States in Afghanistan certainly puts greater pressure on the administration to answer this question in the affirmative, even as the ongoing detention operations at Guantanamo Bay are likely pulling the administration in the other direction. Indeed, the detention of 25 men at Guantanamo for decades without charge or trial may in fact be driving the continuing U.S. reliance on the forever war legal paradigm as applied to Afghanistan. Administration officials have argued in proceedings brought by some of these men that the war in Afghanistan is ongoing, most likely because the only justification under international law for detaining individuals there for decades without charge or trial is if they are being held as part of an ongoing armed conflict. Under IHRL, by contrast, prolonged detention of this nature would violate the detainees’ fundamental human rights.

Even if the United States does not reject the war paradigm as a matter of law in Afghanistan, the withdrawal of U.S. forces will likely lead to greater reliance on the jus ad bellum for any “over-the-horizon” use of force operations there, potentially exposing differences between the United States, allies, and others in the interpretation of jus ad bellum elements. Furthermore, the withdrawal will likely provide greater scrutiny of the United States’ relatively restrictive approach to the role of international human rights law (IHRL) in extraterritorial counterterrorism operations, both with respect to the use of force and to detention issues, especially for those detained at Guantanamo. These developments could, for better or worse, prompt the increased use of what I have elsewhere termed “legalistic national security policies” that help bridge differences in views between the United States and its allies, other states, international organizations (IOs), and non-governmental organizations (NGOs) over the scope of IHL and the interpretation of and role for the jus ad bellum and IHRL in these operations.

Greater Pressure on the Forever War Legal Paradigm

Four U.S. presidents from across the political spectrum have been strikingly consistent in their embrace of a forever war legal paradigm for post 9/11 extraterritorial counterterrorism operations against al-Qaeda and “associated forces.” Despite sending U.S. armed forces home from Afghanistan and declaring the end of the war there, Biden’s speech on Aug. 31, 2021, specifically emphasized that the United States would “maintain the fight against terrorism in Afghanistan and other countries. We just don’t need to fight a ground war to do it. We have what’s called over-the-horizon capabilities, which means we can strike terrorists and targets without American boots on the ground, very few, if needed.”

Secretary of State Antony Blinken made similar remarks, noting that, even though the U.S. “military mission is over” in Afghanistan, the United States will “maintain robust counterterrorism capabilities in the region to neutralize those threats, if necessary, as we demonstrated in the past few days by striking ISIS facilitators and imminent threats in Afghanistan – and as we do in places around the world where we do not have military forces on the ground.”

More recently, Secretary of Defense Lloyd Austin commented that such “over-the-horizon” use of force operations, while “difficult” are “absolutely possible.” Indeed, he observed that they are “effective, and fairly common,” and pointed to recent examples of such operations in Syria.

Even more telling, Biden administration officials have made explicit statements embracing the war paradigm as a matter of law in Afghanistan in litigation involving the Guantanamo detainees. Indeed, the continued detention of 37 men at Guantanamo Bay, especially the 25 who have not been charged within the U.S. military commissions, may be a significant reason the United States is continuing to embrace the war paradigm. For example, in its response to a habeas petition filed by Saifullah Abdullah Paracha, a Pakistani citizen held briefly in Afghanistan and then transferred to Guantanamo in 2004, Biden administration lawyers argued in October 2021—after the withdrawal from Afghanistan—that “the United States remains in active hostilities against al-Qaeda and its associated forces, including in Afghanistan.” In subsequent pleadings in the same litigation, the administration similarly argued that “the record evidence demonstrates that hostilities against al-Qaida and associated forces have not ceased, whether in Afghanistan or elsewhere.” And in briefing materials filed in October 2021 in response to the habeas petition of Assadullah Harun Gul, an Afghan citizen held at Guantanamo since 2007, the administration similarly argued that there is a “current ongoing conflict against al-Qaida and associated forces in areas of Africa and the Middle East, including Afghanistan …. [and] U.S. forces remain engaged in active hostilities with al-Qaida and associated forces in these regions.” (The District Court for the District of Columbia has now granted Mr. Gul’s petition).

It is perhaps not surprising that Biden administration officials have made these statements in the Guantanamo litigation, as their legal justification for continuing to hold the 25 Guantanamo detainees without charge or trial depends on it. Specifically, administration officials ground their authority to detain these individuals in Congress’ 2001 Authorization for Use of military Force (AUMF) and the 2012 National Defense Authorization Act (NDAA), which in turn reflect the principle that detention within an armed conflict may continue for the duration of hostilities, and therefore does not require the traditional guarantees of due process accorded in peacetime. Any justification for continuing to detain the 25 men without charge or trial, in some cases for 20 years, requires acceptance of the idea that the war is ongoing, including in Afghanistan. The issue is of course particularly acute for detainees linked to Afghanistan, for example because they are Afghan nationals or because they fought or were apprehended there (although the United States could argue that, even if hostilities have concluded in Afghanistan, ongoing hostilities elsewhere continue to justify armed conflict detention). 

By clinging to its view of an ongoing, transnational armed conflict against certain terrorist groups, the United States diverges from many other countries, including many of its allies, along with many IOs, NGOs, and commentators. These entities take a more geographically and temporally constrained approach to the question of whether an armed conflict exists in a particular area. In Afghanistan, that approach would likely require a fresh assessment of whether an armed conflict exists between the United States and any terrorist groups operating there now that the United States has withdrawn all military forces, as well as a fresh assessment of whether the Taliban is engaged in an armed conflict or conflicts with terrorist groups. (As the Taliban maintains a close relationship with al-Qaeda, an ongoing armed conflict between the Taliban and al-Qaeda is improbable. A finding of an armed conflict between the Taliban and ISIS or other terrorist groups is much more likely). Nevertheless, such findings, and resulting conclusions about the reach of IHL would probably be much more limited than the view embraced by the United States that an armed conflict between the United States and multiple terrorist groups, including al-Qaeda and ISIS, is ongoing and essentially global.

Increasing Pressure on the Jus ad Bellum Paradigm for Use-of-Force Operations

Even if the United States fails to retreat from the global war paradigm as a matter of law in Afghanistan and therefore continues to apply IHL to any operations it might conduct there, the U.S. withdrawal will likely put more pressure on the U.S. interpretation of the jus ad bellum as it might apply to any “over the horizon” use-of-force operations. Under the core principle of the jus ad bellum enshrined in the U.N. charter and customary international law, a state may not use force in the territory of another state. The jus ad bellum, however, permits three clear exceptions to this rule: consent by the territorial state, a U.N. Security Council Resolution authorizing the use of force, and self-defense. (Only a few states, such as the United Kingdom, would recognize a fourth justification, humanitarian intervention in the event of mass atrocities).  

The United States has said that, if an armed conflict is ongoing, it need not apply the jus ad bellum to every use-of-force operation and often does not do so. However, on the flip side, this assertion implies that the United States does sometimes conduct a jus ad bellum analysis for use-of-force operations even within an armed conflict. Here, it seems likely that the United States will conduct new jus ad bellum analyses for use-of-force operations in Afghanistan because the Afghan government has changed. Prior to the U.S. withdrawal in August, 2021, the U.S. military operated based on the consent exception to extraterritorial operations because of course it had the consent of the Afghan government. Now, however, the Taliban regime governs Afghanistan based on de facto authority, even if many states still have not  recognized the regime as the legitimate government of the country. Therefore, the previous ad bellum justification for use-of-force operations within the territory of Afghanistan is no longer valid. In these circumstances, the United States probably will conduct a new jus ad bellum analysis to justify future use-of-force operations.

In Afghanistan following the U.S. pullout, no current U.N. Security Council resolution explicitly authorizes continuing use-of-force operations against terrorist groups. As to consent, it is perhaps conceivable that the United States could obtain consent from the Taliban regime to conduct operations against ISIS, given that the Taliban is currently fighting against ISIS. (Indeed, the United States collaborated with the Taliban on a limited basis prior to the Taliban takeover and the U.S. withdrawal, and General Milley has said future collaboration is “possible”). Nevertheless, political considerations make explicit consent far-fetched. Indeed, even if the Taliban government were to consent, it most likely could not make such consent public. Furthermore, because the Taliban regime has ongoing ties with al-Qaeda, the United States would not likely seek, nor would the Taliban be likely to grant, consent to operations against al-Qaeda. Therefore, the most likely justification for the United States to use force under the jus ad bellum would be the doctrine of self-defense.  

As a result, any use-of-force operations by the United States in Afghanistan would expose, and perhaps put pressure on, U.S. legal interpretations regarding what counts as self-defense. Set forth in article 51 of the U.N.Charter and customary international law, the doctrine of self-defense provides that a state may use force in the territory of another state if it has suffered an armed attack or is facing an “imminent” armed attack, and any use of force must also be necessary and proportionate. Further, a doctrine articulated most prominently by the United States holds that, in the event of an armed attack or imminent armed attack from a non-state group operating within the territory of another state, the victim state may use force against the non-state group within the territorial state if the territorial state is “unwilling or unable” to effectively address the threat (even absent the latter’s consent or UN Security Council authorization). Finally, article 51 requires any state using a self-defense justification for the use of force against another state to notify the United Nations Security Council.

 Here, it is critical to note that the United States differs from many of its allies in the interpretation of these elements, and differences in the interpretation of “imminence” are particularly pronounced. Whether the relatively recently developed “unwilling or unable” standard has attained the status of customary international law is also contested. As a result, any future U.S. use of force operations in Afghanistan would likely expose differences between the United States and other states, as well as IGOs, NGOs and other entities that might interpret these elements differently. 

Scrutiny of the Meaning of “Imminent Armed Attack” 

The U.S. interpretation of “imminence” is particularly likely to face scrutiny in the context of any new over-the-horizon operations in Afghanistan. The United States has said that, in interpreting what amounts to an “imminent” armed attack, it evaluates factors that include:

the nature and immediacy of the threat; the probability of an attack; whether the anticipated attack is part of a concerted pattern of continuing armed activity; the likely scale of the attack and the injury, loss, or damage likely to result therefrom in the absence of mitigating action; and the likelihood that there will be other opportunities to undertake effective action in self-defense that may be expected to cause less serious collateral injury, loss, or damage.

The United States has said, furthermore, that it may conclude an attack is “imminent” even if there is no specific evidence pointing to the location or nature of an attack, if “there is a reasonable and objective basis for concluding that an armed attack is imminent.” And the United States has asserted that “the traditional conception of what constitutes an ‘imminent’ attack must be understood in light of the modern-day capabilities, techniques, and technological innovations.”

The U.S. view is relatively broad – much broader than the traditional formulation in customary international law, asserted by Daniel Webster in the Caroline case, which requires any threat to be “instant, overwhelming, leaving no choice of means, and no moment of deliberation.” Other states, such as the United Kingdom, have emphasized that they do not accept the expansive view of imminence put forth by the U.S. government.

Because many states and other entities are unlikely to share the U.S. view that it remains in the same armed conflict stemming from the 9/11 attacks in Afghanistan, they are likely to scrutinize any use of force by the United States against terrorist groups in Afghanistan under the jus ad bellum, and any such operation will therefore likely invite discussion and critique of the U.S. interpretation of imminence. Specifically, other countries, IOs, and NGOs may question the U.S. assessment of whether the terrorist groups in question are in fact posing an “imminent threat.” The U.S. drone strike on Iranian Qods Force Commander  Soleimani in January 2020, as well as U.S. strikes against Iran-backed militias in Syria and Iraq, for example, have sparked such debates. (It should also be noted that the assessment of whether or not an attack might be “imminent” is tied into the overarching question of whether or not the use of force is “necessary,” and there is considerable criticism of the U.S. approach to that element of the self-defense doctrine as well).

In Afghanistan, the fact that no U.S. troops remain in the country will likely exacerbate questions raised about any U.S. assessments that terrorist groups in Afghanistan are threatening “imminent” attacks. In other contexts, the United States has justified the use of force in self-defense to protect against attacks on U.S. armed forces in theater. For example, the Biden administration deemed the risk of an attack on U.S. armed forces in theater “imminent” in order to justify strikes on Iran-backed militias in Syria. Without U.S. armed forces in Afghanistan itself, any assessment of an “imminent” attack would need to be based on the risk of attack on U.S. forces stationed elsewhere, other U.S. persons or facilities outside the United States, or on the territory of the United States. All of these remaining contexts are ripe for the United States to apply its relatively broad conception of imminence and therefore expose the differences between the United States and other international actors in interpreting this element of self-defense. 

Debate about Whether Afghanistan is “Unwilling or Unable” to Address the Terrorist Threat?

The U.S. interpretation of the “unwilling or unable” element of self-defense is also controversial. To be sure, many states and other entities have accepted this component of the self-defense doctrine: that, assuming all other elements are met, a state has the right of self-defense when the territorial state is “unwilling or unable” to address the threat posed by a non-state group. But application of this standard to Afghanistan may prove particularly challenging and expose differences between the United States and others in their approach to it. One factor that is used to determine if a state is “unable” to address a threat is whether a non-state group controls territory, as ISIS did in Syria. However, when a group does not control territory—and ISIS now no longer holds territory in Syria, while the territorial holdings of Islamic State Khorasan (ISIS-K), the ISIS affiliate in Afghanistan, are vastly reduced—it is much less clear how this element should be interpreted. 

The United States has articulated a fairly broad interpretation of the “unwilling or unable” test. In its 2016 Report on Legal and Policy Frameworks Guiding the United States’ Use of Military Force and Related National Security Operations, the government suggested that this element could be met when a state “cannot or will not take effective measures to confront a state actor that is using the State’s territory as a base for attacks and related operations against other states.” Although the United States notes that any justification for the use of force on this basis should be “exceptional,” this formulation could be construed quite broadly. For example, the mere fact that a non-state actor has conducted, or perhaps even planned, an attack could suffice. In its recent Article 51 letter to the U.N. Security Council defending the use of force against Iran-backed militias operating in Syria without Syrian government consent, the United States addressed this “unwilling or unable” standard by noting that Syria did not “prevent the use of its territory” as the launching point for attacks by the militias – suggesting a quite expansive reading of this element.

Any use of force by the United States against ISIS-K or affiliated terrorist groups in Afghanistan is likely to provoke questions and debate about the breadth of the U.S. interpretation of this element. Since it emerged in Afghanistan in 2015, the ranks of ISIS-K have dwindled to about 1,500 to 2,200 fighters in small areas of the Kunar and Nangarhar Provinces, but the United Nations estimates that ISIS-K is seeking to revitalize, attract foreign fighters, and “position[] itself as the sole pure rejectionist group in Afghanistan,” a hardline fundamentalist alternative to the Taliban. Although the group does not hold much territory, it has stepped up attacks within Afghanistan, and the Taliban regime is actively fighting the group. Recent U.S. intelligence estimates suggest that, although the risk of attacks on U.S. interests is currently low, ISIS-K is motivated to conduct such attacks. Because the Taliban is combating the group, it be difficult to argue that the regime  is “unwilling” to address the threat posed by ISIS-K, and any legal justification under the jus ad bellum for a use of force against the group would probably depend upon a conclusion that the Taliban regime is “unable” to address the threat. But because ISIS-K’s ’s territorial control is minimal, and because the Taliban have said they can handle the threat posed by the group, any U.S. use-of-force operations against ISIS-K in Afghanistan that relied on such a finding would stretch the meaning of “unable” and likely raise questions about the U.S. interpretation of that element. Any U.S. use of force against al-Qaeda or its affiliates, by contrast, would probably generate less debate, as the Taliban regime has close ties with these groups – such ties could more easily support a conclusion that the Taliban regime is “unwilling” to address threats posed by al-Qaeda.

Debates on the Scope of International Human Rights Law

Any over-the-horizon operations by the United States in Afghanistan, along with the continued imprisonment of Afghanistan-linked detainees at Guantanamo, may also prompt increasing debate on the relatively constrained approach the United States has taken to the scope of its obligations under international human rights law (IHRL) outside the United States, particularly in counterterrorism operations. The withdrawal of U.S. forces from Afghanistan therefore could increase pressure on the United States to recognize the applicability of IHRL to at least some U.S. operations in Afghanistan or with regard to Afghanistan-linked detainees.

While clinging to the war paradigm as a matter of law, the United States has embraced a correspondingly constrained role for IHRL, both because the United States views the scope of IHRL as limited within armed conflict, and because the United States has adopted a restrained approach to the extraterritorial application of IHRL. Many other states, particularly states within the Council of Europe, which are subject to the jurisdiction of the European Court of Human Rights, take a broader view of the extraterritorial reach of IHRL both outside armed conflict and within it, especially as applied to military detention operations. Other entities, such as the United Nations Special Rapporteur on Extrajudicial,  Summary or Arbitrary Execution and the United Nations Human Rights Committee, have adopted an even broader view of states’ extraterritorial IHRL obligations. 

Any use-of-force operations by the United States in Afghanistan would likely expose these differences, because the U.S. justification for acting under IHL, and its arguments that IHL often displaces IHRL as the lex specialis during armed conflict, are now much weaker. Those states and other entities which no longer view IHL as applicable to U.S. operations in Afghanistan and which accept the broad extraterritorial reach of IHRL will likely argue that there is an even stronger case for the more stringent IHRL rules to apply. Specifically, such states and entities will likely contend that, because the United States is no longer engaged in an armed conflict in Afghanistan, IHRL rules that protect the right to life and limit the use of lethal force should govern some extraterritorial use of force operations in Afghanistan. 

Ongoing U.S. military detention at Guantanamo of men linked to Afghanistan, either because they are Afghan citizens or because they were apprehended there, will also likely face greater scrutiny under IHRL now that the U.S. has withdrawn all forces from Afghanistan. As in the case of over-the-horizon use of force operations, the justification for applying the relatively more permissive rules of IHL to wartime detention is now much weaker for many of the detainees linked to Afghanistan. Under the more stringent rules of IHRL—which for example prohibit prolonged arbitrary detention—the  imprisonment of many of the Guantanamo detainees for 20 years without charge is a clear violation. IHRL also mandates due process protections that are currently not provided to the Guantanamo detainees, such as the right to a lawyer without charge. In other words, the long-term imprisonment of Guantanamo detainees without charge would violate many IHRL norms. The reduced justification for holding these detainees under a war paradigm as a matter of law therefore could generate increased criticism of the U.S. failure to abide by IHRL at Guantanamo.

What Next: A Greater Demand for “Legalistic” National Security Policies?

As I have argued elsewhere, both in brief and in greater depth, the United States has across multiple administrations attempted to bridge its differences with many allies, IOs and NGOS over the scope of the war paradigm as a matter of law by adopting “legalistic” national security policies. In embracing a global war paradigm as a matter of law—with a broad role for IHL and a much more constrained role for IHRL—the United States faced significant interpretive differences with allies and other entities even before the withdrawal of U.S. armed forces from Afghanistan. To blunt criticism and improve interoperability, the United States has adopted and maintained, across multiple administrations, standards that move the United States closer to IHRL in its use-of-force and detention operations, but as a matter of policy rather than international law. 

The withdrawal of U.S. forces from Afghanistan, by exposing these interpretive differences – both about the relative scope of the IHL, IHRL and jus ad bellum paradigms, as well as over the content of the doctrinal elements within each of these paradigms, will likely increase the pressure to continue or expand the use of such policies. In other words, it is quite possible that we will see the Biden administration refine policies such as those on the use of force to emphasize that, as a matter of policy rather than law, the United States will follow higher standards than those set forth in IHL in future use of force operations in Afghanistan. 

More broadly, now that the United States has withdrawn all U.S. forces from Afghanistan, the Biden administration faces a series of tough legal questions: In Afghanistan, will the United States finally abandon the forever war legal paradigm for counterterrorism? Will the United States embrace a broader scope for IHRL and the jus ad bellum for operations linked to Afghanistan? And if the answer to these first two questions is no, will the administration use policy guidance to address the points of tension that are sure to arise as the United States conducts counterterrorism operations related to Afghanistan?  

The jury is still out on all these questions. The Biden administration’s contorted legal argumentation in the Guantanamo litigation suggests that, as long as Guantanamo remains open, it will be hard for the United States to leave the war path, including in Afghanistan. But isn’t it high time for the United States to pull back from the global war paradigm for counterterrorism as a matter of law, and not just policy? Certainly, the case for closing Guantanamo as quickly as possible has never been stronger.

Image: US vehicle is pictured at a military base in Rumaylan (Rmeilan) in Syria’s northeastern Hasakeh province on July 28, 2020. (Photo by DELIL SOULEIMAN/AFP via Getty Images).