While one person’s judgment can be quite elastic, the president’s need not be in order to make the AUMF extremely capacious. It is broad on its own terms. For example, al-Qaeda is the organization that was principally complicit in 9/11, and thus it may be attacked anyplace, anytime. The AUMF also undoubtedly authorizes warfare against the Taliban, al-Qaeda’s former host, even though the president, in his discretion, chooses not to regard the Taliban as an enemy — indeed, our government has not even designated the Afghan Taliban as a terrorist organization, much less declared war against it. In addition, the AUMF would authorize war against Iran. The 9/11 Commission all but expressly implicated the mullahs in the 9/11 plot, despite the disinclination of President Obama, of President Bush before him, or of Congress to connect those dots.

Nevertheless, as broadly as the 2001 AUMF could be interpreted, it is not boundless. It clearly requires any use of force to be rooted in 9/11. Only those who plotted and executed the 9/11 attacks, or who harbored those who did so, are legitimate targets.

Some claim there is more play in the AUMF’s joints. They point out that the AUMF goes on to explain Congress’s desire “to prevent any future acts of international terrorism against the United States.” But this is an explanation of Congress’s motive for the authorization spelled out in the AUMF; it does not expand that authorization. Of course it is true that, 9/11 aside, Congress does not want terrorists to attack us. But that does not alter the fact that, in the AUMF, Congress permitted combat operations only against terrorists culpable for 9/11, not against any terrorist who might ever attack us. Even the reference to “future acts of international terrorism” seized on by expansive constructionists is expressly limited to acts that might be committed “by such nations, organizations or persons” complicit in the 9/11 attacks or in the harboring of 9/11 attackers.