President Obama says he would “welcome congressional support” but does not need authorization from Congress in order to use force against the Islamic State. The President appears to have taken no steps to propose actual language to Congress or to move the idea of an authorization along. And Congress appears to have done nothing significant as a body concerning an authorization of force. Late last month Speaker John Boehner said that Congress would vote on an authorization as soon as the President asked for one. “The president typically in a situation like this would call for an authorization vote and go sell that to the American people and send a resolution to [Capitol] Hill,” Boehner told ABC. “The president has not done that. He believes he has authority under existing resolutions to do what he’s done.”

Many people think Boehner is ducking for cover, and maintain that Congress should act on its own initiative, even without a presidential request, to authorize force against the Islamic State. “Since when do we sit around waiting, using the excuse ‘He didn’t ask’?” asked House Minority Leader Nancy Pelosi last week. “No, if you want to have an authorization that has any constraints on the president, you don’t wait for him to write it.” Former Representative Tom Campbell claims that Congress’s inaction amounted to “running way from its responsibility.”

The truth is that neither the President nor the leadership in Congress wants a vote right now. But the very notion that Congress is going to authorize force in the absence of a concrete presidential proposal and a significant presidential push to see it enacted is fanciful. Congress is naturally responsibility-dodging. And on top of that, its de-centralized structure makes it very hard for it to get its act together, on its own initiative, to authorize force. I suspect that this has been generally true for all of American history. But I have looked only at the post-World War II period.

Since World War II, six of the eight congressional authorizations to use force resulted from a formal request by the President to Congress, including essential terms and usually a draft proposal, all followed by executive branch engagement with Congress to see it through. (The cases are: Formosa (1955), Taiwan (1957), Vietnam (1964), Iraq (1992), post-9/11 (2001), and Iraq (2002).) Presidents affirmatively sought congressional support in these cases regardless of whether the President’s party controlled one or both houses of Congress, or neither. Presidents did not get all of what they wanted in these cases, but they got most of what they wanted. There are two exceptions where Congress initiated the authorization—in Lebanon (1983) and Somalia (1993). But these are not happy precedents for the presidency, for they are instances in which presidential unilateralism went badly, and Congress in response took the initiative to insist on the applicability of the War Powers Resolution and to authorize force with President-constraining conditions.

In modern times, in sum, AUMFs have materialized in two situations: (1) Presidents affirmatively seek and make the case for congressional support, they propose terms, and they push hard for enactment on the president’s terms; or (2) Presidents act unilaterally, something goes wrong, the conflict becomes unpopular, and Congress pushes back with a conditional authorization and an insistence on the applicability of the WPR...