Legal framework for the U.S. use of military force since 9/11.

Author:Preston, Stephen W.
Position:Proceedings of the 2015 Annual Meeting of the American Society of International Law: Adapting to a Rapidly Changing World

This policy address was given at 5:00 p.m., Friday, April 10. The speaker was Stephen Preston of the U.S. Department of Defense.


Thank you, Professor Damrosch, for that kind introduction and for the invitation to be here this afternoon. As a leader in ASIL, a professor of international law, and for many years editor of the American Journal of International Law, you have played a central role in shaping our understanding of international law. And you have done so with an eye to the practical realities faced by the government lawyer, which has made your contributions all the more meaningful. I also want to thank Mark Agrast and Wes Rist, who have done so much to make this event, and my participation in it, possible.

I am grateful, as well, to my colleagues in government, who have contributed to my remarks today in many ways--not least through the wisdom, learning, and hard work they have brought to bear in answering the difficult questions we regularly face together. Finally, I want to thank all of you--the members of the American Society of International Law assembled here this afternoon--for the warm reception I have received and, more important, for your keen interest in the legal issues affecting the national security of our country. I am very pleased to have the opportunity to speak with you today. Indeed, I am greatly honored.

The Department of Defense has a long history of engagement with the American Society of International Law. The first and longest-serving president of the Society, Elihu Root, served as Secretary of War under two presidents before founding the Society in 1906. He saw this organization as a place where the hard issues of the day could be discussed and debated. And he believed that by educating the American public about international law, the rush to war could be slowed. As he once put it, "[i]n the great business of settling international controversies without war ... essential conditions are reasonableness and good temper, a willingness to recognize facts and to weigh arguments which make against one's own country as well as those which make for one's own country." (1) I could not agree more.

The theme of this year's annual meeting, "Adapting to a Rapidly Changing World," is a pretty good description of our day-to-day job at the Defense Department. The conflicts and threats we face are constantly shifting and evolving. Today, I will discuss how the U.S. government has responded to this rapidly changing world and, specifically, how the legal framework for our military operations has developed since the attacks of 9/11.


President Obama has made clear from the beginning of his presidency that he is deeply committed to transparency in government because it strengthens our democracy and promotes accountability. Although a certain degree of secrecy is of course required to protect our country, the administration has demonstrated its commitment to greater transparency in matters of national security and, specifically, in explaining the bases, under domestic and international law, for the United States' use of military force abroad. We have seen this in the president's own speeches, for example, at the National Archives in May 2009, at National Defense University (NDU) in May 2013, and at West Point in May 2014.

Among senior administration lawyers, we saw this early on, in a speech by the State Department's Legal Adviser at ASIL in March 2010--this same meeting, five years ago-- and in later speeches by the Attorney General at Northwestern in March 2012, and by my predecessor as Department of Defense General Counsel at Yale and at Oxford, both in 2012. There was even a very modest contribution by the CIA General Counsel in remarks at Harvard Law School in April 2012. My remarks here today are the latest in the series--an update of sorts--addressing the legal authority for U.S. military operations as the mission has evolved over the past year or so.

This talk will proceed in four parts. First, I want to review the legal framework for the use of military force developed in the aftermath of the 9/11 attacks. Second, I will explain the legal basis for current military operations against the so-called Islamic State of Iraq and the Levant, or ISIL. Third, I will discuss the end of the U.S. combat mission in Afghanistan and its impact on the legal basis for the continuing use of military force under the 2001 AUMF. Fourth, and finally, I will look ahead to the legal framework for counterterrorism operations in the future.


Let us begin with a bit of history. It is only by seeing where we have been over the past decade and a half that we can understand where we are today.

Return to the first days after the attacks on September 11, 2001, for it is in that time that our government began to articulate the legal framework that we still rely on today. As many of you know, it was only days after the 9/11 attacks that Congress passed, and the president signed, an authorization for the use of military force, or AUMF, authorizing the president to take action to protect the United States against those who had attacked us. Even though it was only days later, we already knew that the attacks were the work of Al Qaeda, a terrorist organization operating out of Afghanistan, led by a man named Usama bin Laden.

The authorization that was enacted into law--which came to be known as the 2001 AUMF--was not a traditional declaration of war against a state. We had been attacked, instead, by a terrorist organization. Yes, the Taliban had allowed bin Laden and his organization to operate with impunity within Afghanistan. But it was not Afghanistan that had launched the attack. It was bin Laden and his terrorist organization.

The authorization for the use of military force that Congress passed aimed to give the president all the statutory authority he needed to fight back against bin Laden, his organization, and those who supported him, including the Taliban. At the same time, the 2001 AUMF was not without limits. It authorized the president to "use all necessary and appropriate force against those nations, organizations, or persons he determines planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, or harbored such organizations or persons, in order to prevent any future acts of international terrorism against the United States by such nations, organizations or persons." (2)

With this statutory authorization, the United States commenced military operations against Al Qaeda and the Taliban in Afghanistan on October 7, 2001, notifying the UN Security Council consistent with Article 51 of the UN Charter that the United States was taking action in the exercise of its right of self-defense in response to the 9/11 attacks.

Although the 2001 AUMF was not unlimited, enacted as it was just a short time after the attacks, it was necessarily drafted in broad terms. Shortly after President Obama came into office, his administration filed a memorandum in Guantanamo habeas corpus litigation offering the new president's interpretation of his statutory authority to detain enemy forces as an aspect of his authority to use force under the 2001 AUMF. That memorandum explained that the statute authorized the detention of "persons who were part of, or substantially supported, Taliban or Al Qaeda forces or associated forces that are engaged in hostilities against the United States or its...

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