US airstrikes ISIS in Iraq have now begun. There may well be good moral and strategic rationales for the president’s action. But there are still serious questions about his legal authority to order it. There are several possible legal justifications for the airstrikes. But none can justify more than very limited military action without additional congressional authorization.

The Obama administration has not yet put forward an official legal rationale for its actions. Cornell professor Sarah Kreps predicts that it will probably rely on the president’s inherent powers as commander in chief of the armed forces under Article II of the Constitution. If it is adopted, this theory is vulnerable to the objections I made in my last post. The commander-in-chief Clause makes the president the highest ranking general and admiral, but does not give him the power to initiate war without congressional authorization.

Perhaps the president would not need congressional authorization if all he seeks to do is protect US personnel already in Iraq from attack. But the President’s speech last night clearly indicates that he intends to go beyond this, as he also emphasized the need to prevent ISIS’ attempted genocide of the Yazidi minority. Michael Ramsey, a leading academic expert on constitutional war powers, reaches a similar conclusion (see here and here).

As I noted in my earlier post, congressional authorization might not be required for very small-scale airstrikes that are not extensive enough to qualify as a war. So far, I don’t think that threshold has yet been crossed. But there is a real chance it will be soon.

Harvard Law Professor Jack Goldsmith suggests that the president has the authority to launch airstrikes under the 2002 Authorization for the Use of Military Force against Iraq. As Jack points out, the text of the resolution is not limited to military action against Saddam Hussein’s regime, but covers all military action the president “determines to be necessary and appropriate in order to . . . defend the national security of the United States against the continuing threat posed by Iraq.” Perhaps ISIS can be considered a part of the “threat” in question.

This is clever legal reasoning. But I don’t think the language is quite as broad as Jack suggests. It does not authorizes the use of force against all threats emanating from Iraq, but merely “against the continuing threat.” In other words, the threat in question must have some continuity with and connection to Saddam Hussein’s regime. This reading is also consistent with the text of the resolution as a whole, which extensively discusses the various dangers posed by Saddam, and does not mention any other potential threats.

The 2002 AUMF was surely broad enough to justify waging war against Saddam and against other groups that resisted the US invasion and occupation of Iraq in the aftermath of his overthrow. But it is not broad enough to justify entering a new conflict some three years after US combat forces have been removed. Moreover, as Jack points out, the Obama administration is highly unlikely to rely on the 2002 AUMF, which it has previously stated should be repealed.

It might also be argued that military action against ISIS was authorized by the 2001 AUMF adopted in the wake of the September 11 attacks, giving the president authority to wage war against “organizations, or persons . . . [who] planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001.” But, as Jack notes, it is a major stretch to shoehorn ISIS into that category, given its break with al Qaeda.

Some international law scholars argue that nations have a special responsibility to combat major crimes against humanity, especially genocide. President Obama himself described ISIS’ actions as “genocide” in his speech announcing the authorization air strikes. I don’t doubt the accuracy of that description, given ISIS’ massacres of Christians and Yazidis. Perhaps this is a sufficient justification for intervention under international law. But the Constitution does not exempt wars waged for the purpose of preventing genocide from the requirement of congressional authorization. At Opinio Juris, international law scholar Julian Ku suggests that today’s action, combined with the 2011 Libya war, may create a precedent for a presidential power to unilaterally authorize “humanitarian intervention.” But the Obama administration has not put forward any such general theory of presidential power. And any attempt to do so would go against the text of the Constitution.

Given the dire situation in Iraq, some might dismiss legal concerns about the authority for US military intervention as irrelevant technicalities. But constitutional limits on presidential war powers are not just legalistic quibbles. They protect us against entering wars without a broad political consensus in favor of them. That reduces the likelihood of entering an unwise conflict at the behest of a single leader and his ideologically homogenous advisers. Broad political support also increases the chances of winning once the war actually begins.

UPDATE: In a background briefing last night, a “senior administration official” stated that Obama will indeed rely on the Article II Commander-in-Chief Clause as justification. This is not yet an official formal statement of the administration’s position. But it is certainly suggestive:

As to the domestic legal basis, we believe the President has the authority under the Constitution as Commander-in-Chief to direct these actions, which are consistent with this responsibility to protect U.S. citizens and to further U.S. national security and foreign policy interests. Specifically, the protection of U.S. personnel and facilities is among his highest responsibilities as Commander-in-Chief, and given the threats that we see on the periphery of Erbil, he has authorized the use of targeted military action.
Similarly, we believe that there is an urgent humanitarian challenge that further poses a threat to U.S. interests. As I said this rises to the level of a potential act of genocide when you have an entire group of people being targeted for killing, and you have a population of the size that is on Mount Sinjar that is threatened with starvation as one option, or, as the President said, coming down that mountain and potentially being massacred by ISIL.

I agree that the president has the power to order military action to defend “US personnel and facilities” against attack. But there is no unilateral presidential authority to wage war to protect any and all American “national security and foreign policy interests,” including “humanitarian challenges.” As then-Senator Obama put it in 2007, ” “[t]he President does not have power under the Constitution to unilaterally authorize a military attack in a situation that does not involve stopping an actual or imminent threat to the nation.”