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American Journal of International Law


In the fifteen years since the Authorization for Use of Military Force (AUMF) was enacted on September 18,2001, the Taliban has been removed from power but not eliminated; Osama Bin Laden has been killed and the senior leaders of Al Qaeda as of 9/11 have been captured,killed, or driven underground, although Al Qaeda remains a threat; numerous Al Qaeda affiliates have sprung up around the globe, most notably in Iraq, Yemen, Syria, and Somalia; and most ominously, the Islamic State has arisen from the ashes of Al Qaeda in Iraq to become what the Director of National Intelligence has described as "the preeminent terrorist threat" against the United States "because of its self-described caliphate in Syria and Iraq, its branches and emerging branches in other countries, and its increasing ability to direct and inspire attacks against a wide range of targets around the world."1

Despite massive changes in the geographical scope of the conflict that began on 9/11, the strategy and tactics employed, and the identity of the enemy, the AUMF remains the principal legal foundation under U.S. domestic law for the president to use force against and detain members of terrorist organizations. The AUMF is already the longest operative congressional authorization of military force in U.S. history, and, as of fall 2016, there was no immediate prospect that Congress would move to repeal or update it. With the continued vibrancy of Al Qaeda, its associates, and the Taliban, and with the 2014 presidential extension of the AUMF to cover military operations against the Islamic State, the AUMF is likely to be the primary legal basis for American uses of force for the foreseeable future.

The transformation of the AUMF from an authorization to use force against the 9/11 perpetrators who planned an attack from Afghanistan into a protean foundation for indefinite war against an assortment of terrorist organizations in numerous countries is one of the most remarkable legal developments in American public law in the still-young twenty-first century.As this article demonstrates, this transformation largely occurred during the Obama presidency. Given all that has happened since 9/11, it is easy to forget that almost every issue about the AUMF's meaning and scope remained unresolved at the end of the Bush presidency. It was during Obama's time in office, guided by his administration, that courts construed the AUMF to resolve many of its ambiguities and uncertainties, and that Congress ratified the basic frame-work of these judicial interpretations. The Obama administration also relied extensively on the judicial construction of the AUMF, supplemented by its own elaborate and publicly expressed interpretations, as a basis for targeting members of various terrorist organizations in numerous countries. Furthermore, the administration significantly extended the scope and duration of the AUMF by interpreting it to apply to the Islamic State.

In a real sense, then, the 2001 AUMF is President Obama's AUMF. Despite his frequent rhetoric about ending the AUMF-authorized conflict, part of Obama's legacy will be cementing the legal foundation for an indefinite conflict against various Islamist terrorist organizations. After making these points in parts I and II, we examine in part III the role that international law has played in informing the content of Obama's AUMF. The Obama administration maintained that the international laws of war- both jus in bello and jus ad bellum-were important constraints on its actions under the AUMF. There are many disputes and uncertainties, however, about how to apply the laws of war to a global noninternational armed conflict against terrorist organizations. For these unsettled issues of international law, the administration often adopted interpretations that supported presidential discretion and flexibility, and thus that enhanced rather than constrained the administration's authority to take action under the AUMF.

We should emphasize at the outset that our goal here is descriptive, not normative. Our aim is to capture how the meaning and scope of the AUMF developed during President Obama's time in office-primarily due to interpretations and actions by his administration, but also as a result of important decisions by the judiciary and Congress. Identifying the distinctive contributions made to AUMF jurisprudence during the Obama administration is, we think, a necessary prerequisite to any normative assessment of the evolution of this body of law.

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