In tonight’s speech on the struggle against ISIS, President Obama stated that the United States will wage “a systematic campaign of airstrikes against these terrorists.” He also made clear that the campaign is also likely to extend to Syria, as well as Iraq. There is likely good reason for the US – working with other nations – to take military action against ISIS. The president is right about that. But for reasons I outlined here and here, any such extensive military campaign qualifies as a war that requires congressional authorization under the Constitution. Article I of the Constitution gives Congress, not the president, the power to initiate war. If the air strikes last more than 60 days, they also require authorization under the War Powers Act of 1973.

In recent days, the administration has taken to arguing that they already have congressional authorization under the 2001 Authorization for the Use of Military Force, which gives the president the authority 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, 2001, or harbored such organizations or persons.” The administration has – justifiably, in my view – interpreted this to cover forces “associated” with al Qaeda as well as al Qaeda itself. But as Benjamin Wittes of the Brookings Institution points out, that is not enough to cover the campaign against ISIS, because al Qaeda and ISIS are not allies or associates at all, due to their mutual hostility:

I have always supported the administration in taking a broad view of what it means to be an “associated force” under the AUMF. But “associated” does not mean “not associated” or “repudiated by” or “broken with” or even “used to be associated with.”

This is not a stable or sustainable reading of the law, absent some dramatic, non-public intelligence about the ISIS-Al Qaeda relationship. Remember that this is a law that barely a year ago, President Obama was lecturing us needed to be narrowed and repealed. “This war like all wars must end,” he piously intoned. Apparently not, however, before we dramatically expand its interpretive scope and deploy it to support a new and open-ended military campaign that, in the president’s own words, “will take time.” All to avoid asking the girl, who might say no, to dance.

Some defenders of the administration, such as legal scholar Peter Spiro, argue that the campaign against ISIS does not need congressional authorization because it is not a “real war,” primarily because the president assures us it will be limited to air strikes and probably won’t involve a risk of significant US casualties. The president himself said tonight that the campaign against ISIS “will not involve American combat troops fighting on foreign soil.” Such arguments are difficult to credit. Air attacks are among the most important instruments of modern warfare, and Air Force and Navy pilots surely qualify as combat troops; and it’s hard to see a meaningful distinction between “fighting on foreign soil” and bombing foreign soil. Repeated air strikes intended to – as the President put it – “degrade, and ultimately destroy” a potent enemy force that controls a great deal of territory, qualify as war by any reasonable definition. Claims that large-scale air attacks don’t count as warfare were specious when the administration trotted them out in defense of its intervention in Libya in 2011; and they have not improved with age. You don’t have to be a constitutional law professor, like the president, to see that.

Legal arguments aside, getting congressional authorization is also valuable because it can help develop the kind of broad political support that makes it more likely that we will persist and succeed in the campaign despite possible setbacks. If the going gets tough, the tough are more likely to get going if they have broad support from the public and political elites.

In this case, unlike his plan to launch strikes against the Assad regime in Syria last year (when he unsuccessfully sought congressional authorization), Obama actually does have broad support for acting against ISIS, including from most Republicans. The arguments Obama himself made in defense of going to Congress then apply with equal force today.