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New War, Same Problem: Why the AUMF Needs To Be Updated

By: Joseph Epstein

The United States Department of Defense has been conducting extensive operations throughout Africa against several different terrorist organizations, including al-Shabab and branches of ISIS. The strikes have been justified as a continuation of the war on terror; authorized domestically under the 2001 Authorization for the Use of Military Force (AUMF) and internationally in accordance with the laws of armed conflict. However, by extending the 2001 AUMF to justify operations to combat ISIS—and other groups in parts of North Africa—the result is the inclusion of terrorist organizations neither in existence nor contemplated by Congress in the immediate aftermath of the September 11.

Concerns about how the AUMF is being used are not merely partisan in nature but legally relevant: the two main concerns going forward are whether the AUMF continues to provide sufficient legal grounds to justify the use of lethal force under international law and the detention of foreign fighters, not originally contemplated, under domestic law.

Under domestic authority, designated terrorist groups have been detained and their infrastructures have been targeted both in Afghanistan—the home base of al-Qaeda and the origins of the 9/11 attacks—and throughout the Middle East and North Africa, largely under the umbrella of the AUMF as an outgrowth of the war against al-Qaeda and associated forces. As the scope of the mission changes, the legal authority will have to adapt alongside. In a line of decisions starting in 2002, the Supreme Court outlined the parameters of the government’s detention authority, giving general deference to the government to conduct the conflict but not eliminating the due process requirements. There has not yet been a significant challenge to the authority of the AUMF’s expansion to cover ISIS, but it is still possible that a meaningful case will find its way to the D.C. Circuit in the near future. The pending case of ACLU v. Mattis could potentially challenge the government’s authority, under the AUMF, to detain a U.S. citizen fighting abroad for ISIS. The ACLU contends that the unnamed citizen has been illegally detained because the AUMF does not cover ISIS, a contention that Congress could render moot by rewriting, expanding, or reaffirming the AUMF applies to ISIS. The crux of their argument is that the nexus connecting ISIS to the original targets of the bill no longer exists in a meaningful fashion, but the courts have been deferential to governmental determinations of what constitutes an armed conflict. However, Justice O’Connor’s opinion in Hamdi v. Rumsfeld has left the door open for the court to reconsider the issue “[i]f the practical circumstances of a given conflict are entirely unlike those of the conflicts that informed the development of the law of war, that understanding may unravel.”

While the United States was clearly in an armed conflict with a reasonably definable enemy in the Taliban and al-Qaeda when the AUMF was first authored, that clarity has faded away leaving the United States vulnerable to claims that it is out of step with international norms. The current conflict is conducted under the laws of armed conflict, the targeting and detention authorities have been subject to less stringent legal constraints. There is not yet an agreed upon threshold for what constitutes victory against a terrorist group; efforts to date have focused on degrading the operational capacity of these groups and depriving them of leadership, experience, and expertise. How the conflict is defined determines the legal authority that governs. Under the prevailing theory, the use of lethal force has been conducted under the laws of war—jus in bello—as defined by customary international law. Practically, this means that U.S. actions are subject to the standards applied during an armed conflict as opposed to the narrower restrictions of self-defense, though there is not a clear standard it is generally understood to be more limited than the laws of armed conflict.

Recent trends suggested that the United States could move towards a self-defense model to justify its operations, but this too poses concerns legally, politically, and operationally. In Somalia, the escalating conflict against al-Shabab has been justified under a theory of self-defense, stretching traditional and legal concepts. The vast deployment of U.S. forces around the globe, many to hostile and conflict-prone areas, has increased the chances that the forces will come under threats outside the scope of their missions. While self-defense would arguably provide the United States the legal flexibility to quickly respond to its evolving campaign against different terrorist organizations, it would alternatively impose restraints on the scope of legal authority. Furthermore, self-defense has typically been viewed at least internationally as a responsive, or at the very most a limited proactive right. The anticipatory application of self-defense as an offensive campaign runs contrary to this traditional understanding and potentially could place the United States on the wrong side of international norms.

How the U.S. decides to classify the evolving war on terror will impact not just how the specific war against al-Qaeda and its affiliates are understood in terms of the existing framework of international norms but will also shape the evolving field of armed conflict against stateless actors. The concept of a pure self-defense model would drastically change how the international community understands what constitutes a legitimate armed conflict, potentially expand, limitlessly the scope of the war on terror and undermining the prohibition on aggressive wars. By proactively applying the lessons learned from the use—and possible misuses—of the 2001 AUMF, the United States legislature can and should craft a new bill defining the scope of the new phase in the global war on terror. Domestic authorization to pursue terrorism abroad will not only satisfy the American public but present the legal framework consistent with existing international law and providing the international legitimacy necessary to pursue the global conflict.


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