Guest Post: The AUMF and IHL at the Inflection Point

January 2014 - The American flag flies over US detention facility at Guantanamo Bay, Cuba. ICRC/Anna Nelson

January 2014 - The American flag flies over US detention facility at Guantanamo Bay, Cuba. ICRC/Anna Nelson

By Professor Bobby Chesney

University of Texas School of Law

My thanks to the ICRC for sponsoring this discussion, and to the ICRC's Gary Brown, in particular, for his insightful opening post. As Assistant Secretary of Defense (SO/LIC) Michael Lumpkin recently said in Congressional testimony, “we are at a natural inflection point” with respect to the 2001 Authorization for the Use of Military Force (AUMF), and should be taking stock of whether and how it ought to be changed. That seems right to me. We are drawing down in Afghanistan, after all, yet also talking about maintaining (at the very least) capabilities in or near the area that may continue to pursue counterterrorism missions. Al Qaeda remains in existence, yet the question of just which individuals and groups fall under that heading is more vexing than ever—particularly in light of the ongoing proliferation of local armed groups which may or may not have command-and-control ties to the remnants of al Qaeda’s senior leadership. And, of course, there has been much talk in the United States about the AUMF itself, with suggestions ranging from repeal to renewal. 

One pressing question is what all of this might mean for the relevance of IHL to US counterterrorism activities? That general issue has been controversial for the past dozen years, of course, and it’s likely to become more so over time in light of the factors mentioned above. And, so, I thought I might try to lend some focus to the discussion by taking on a set of very specific questions that readers might have in mind. 

Let’s start at the very beginning. When Congress passed the AUMF in 2001, did that domestic legal action suffice, standing alone, to make IHL applicable as a matter of international law?

No. When it comes to IHL’s field of application, one of the great innovations of the modern era was the adoption of an objective, factually-oriented trigger for determining when IHL applies. When the facts on the ground amount to armed conflict, a state’s opinion to the contrary can’t stop IHL from applying. By the same token, if the facts don’t amount to armed conflict, then you generally can’t make IHL applicable as a matter of international law (except perhaps through the issuance of a full-fledged “Declaration of War” between states, as contemplated in Common Article 2 of the 1949 Geneva Conventions).

Naturally, this approach puts tremendous weight on the question of which factors are relevant to the determination whether armed conflict exists (and, perhaps even more so, on the question of how each such factor is to be calibrated). I won’t attempt to restate all that can be said on this complex topic here (though I will note that Nils Melzer has a nice discussion at pp. 243-57 of Targeted Killings in International Law (Oxford 2008)). Suffice it to say that in the context of what might be a non-international armed conflict (NIAC), relevant factors include the existence of both (i) a sufficiently-organized armed group as the ostensible non-state party to the conflict and (ii) sufficiently-intense violence of the requisite nature (as measured with reference to elements such as lives lost and the nature of the means employed by the parties). I’ll note, too, that the ICTY in Tadic emphasized that the violence also must be protracted over time, though Melzer advances the more-nuanced view that the temporal element is relevant, yes, but not a necessary condition in itself.

So, what does it all mean with respect to the fact that Congress passed an AUMF in September 2001? It means that that action, standing alone, was not a sufficient condition to make IHL applicable—and by extension, that the AUMF’s continued existence today is not a sufficient condition, standing alone, to make IHL applicable.  Passage of an AUMF is, to be sure, a strong clue that the US government might employ military means. But in the final analysis, it is the nature and scope of the actual resort to military tools—not the domestic law embrace of authority for such tools to possibly be used— that really matters. That, plus the nature and scope of the actions taken by the other side, of course. 

Ok, but wouldn’t repeal of the 2001 AUMF matter with respect to IHL’s relevance?

No, for the same reasons just stated. The formalities of U.S. domestic law relating to the Constitution’s separation of powers (between President and Congress) regarding authority to decide to use armed force certainly matter on many dimensions. In addition to weakening the domestic law foundation for a president to use force, repeal of the AUMF would have substantial political and diplomatic ramifications tending to make it harder to use force—all the more so if the action terminating the AUMF is accompanied by language that evidences belief that the factual circumstances no longer support a conclusion that armed conflict exists. That is, the government might box itself in, rhetorically, to a position on the factual details that preclude it from claiming that an armed conflict still exists. But the analysis still must turn on those factual details themselves, and in theory those details might yet support an armed-conflict claim. 

To appreciate why I say this, you have to bear in mind an important point that may not be familiar to non-American readers: AUMFs are not the only vehicles in American law that can provide the domestic law justification for using military force. While there is plenty of debate about how wide the authority ranges, there is no question that presidents have some amount of inherent authority to use force on their own initiative under Article II of the Constitution. This authority extends at least to some self-defense scenarios, and it was in this mode that the United States prior to 9/11 used cruise missiles to attack al Qaeda’s senior leadership in Afghanistan. This is why the administration has noted that some form of military option would remain on the table even in a post-AUMF world, in order to address “continuing” and “imminent” threats. As I explain at length in my essay “Postwar", the U.S. government’s understanding of what such authority might entail is ample enough, in theory, to match the nature and pace of drone operations that we see today in places like Yemen and Pakistan. Were that authority to be used in a post-AUMF world, then, the argument for IHL’s relevance might not be appreciably different than how things stand today.

The bottom line is that one should not use the existence (or not) of the AUMF as a necessary or sufficient condition to determine whether IHL applies. One should instead look to the factual circumstances, including and in particular, the nature and intensity of the means employed by the US against specific armed groups and the nature and intensity of the means employed by those groups in turn.  

Ok, but let’s assume the best reading of the factual circumstances is that the IHL threshold is not met. And then a drone strike occurs in, say, Yemen. Would International Human Rights Law (IHRL) then govern the international law analysis of that strike?

As I suspect most readers of this blog already know, the U.S. government takes the view that IHRL has no bearing on its drone strikes for at least two reasons, only one of which (the lex specialis argument) requires the existence of armed conflict. With or without a claim of armed conflict, the U.S. government famously (or infamously, in the view of some) takes the position that its IHRL obligations simply do not apply outside the formal territory of the US. With or without an AUMF, and with or without a plausible claim that there is a state of armed conflict, this won’t change anytime soon.

Wait, does that mean that absent a plausible claim of armed conflict implicating IHL, the U.S. government would view itself as free to act without international legal constraint in conducting a drone strike?

Not exactly. First, the U.S. military applies IHL as a constraint on all of its operations—whether legally required to do so or not—as a matter of long-standing departmental policy. This helps address the risk that the anti-extraterritorial position on IHRL could result in a posture of no-constraint in cases of force below the armed-conflict threshold.  Apparently, the CIA takes the same position, for what that is worth. Second, in any setting involving non-consensual force on the territory of another state under color of Article 51 self-defense, jus ad bellum constraints of necessity and proportionality are in play as well. 

Bobby Chesney is the Charles I. Francis Professor in Law at the University of Texas, as well as the Director of the university’s RobertS.StraussCenter for International Security and Law. He blogs at, and also is on Twitter @bobbychesney. The views expressed in this post are his own and do not necessarily reflect those of the International Committee of the Red Cross.

This post is part of a four-part series on IHL & the AUMF, as well as a wider, ongoing series looking at the contemporary challenges facing IHL. Next week, guest blogger Jennifer Daskal will offer up her views on the topic.