If America is to go to war against ISIS, Congress must vote first. That's the law.

But as the Huffington Post reported, the chances of a congressional vote aren't great. We're in the midst of campaign season, making members of Congress even more reluctant than usual to vote on war.

So what happens if Congress holds no vote? The answer is clear: Without a vote, there can be no war against ISIS. Without proper authorization, President Obama cannot legally pursue military action. And if he does anyway, Congress should make him stop.

One of the worst parts of the hysterical overreaction to the traumatic attacks of September 11 was the Authorization for Use of Military Force, a sweeping law that allows the president to use "necessary and appropriate force" against anyone who "planned, authorized, committed, or aided" the 9/11 attacks. That's extraordinarily broad. It's long since time that statute was updated with much more specific and limited goals.

But as Bruce Ackerman explains in detail, this new war against ISIS stretches even the extremely wide-ranging language of the AUMF past the breaking point. Remember, that statute authorizes the use of force against those who "planned, authorized, committed, or aided" the 9/11 attacks. Well, ISIS did not even exist back then, and it has publicly broken with al Qaeda. What's more, despite the broad language of the AUMF, Congress actually refused to give President Bush the kind of almost limitless language he wanted (enabling preemptive attack against basically anyone) with the explicit desire that the executive come back to Congress for another vote if the president wanted another war.

The administration isn't even going to release its legal reasoning on why President Obama supposedly has the authority to go to war on ISIS. It's easy to see why — because it's a pack of ridiculous sophistry.

The law is straightforward: If there is no congressional vote, according to the War Powers Act, the president gets 60 days before he must have approval to continue using force, and then another 30 days if he doesn't get it. Since he gave notice on Aug. 7, that gives him until Oct. 6 to get approval to continue using force. If he doesn't get it, then he must withdraw by Nov. 5.

This is highly reminiscent of the 2011 "intervention" against Libya. Back then, Obama also insisted that he didn't need congressional authorization but sought a fig leaf vote from Congress. When they voted him down, he just ignored the legislative branch and went right on ahead, claiming ludicrously that the intervention somehow didn't count under the War Powers Act. Naturally, after this sharp insult to their legitimacy as a co-equal branch of government, Congress just forgot all about it.

Greg Sargent reports that the House leadership may push through a vote funding Obama's anti-ISIS program, thus allowing them to weasel out of a direct vote on the war itself. That would be worst of all, giving an effective congressional stamp of approval without actually fulfilling the letter of the law, or delimiting a clear agenda for what the president is allowed to do.

This almost certainly won't happen, given the decrepitude of the institution, but Congress should really press the president on this. Have a debate and pass a law saying what he is allowed to do, if anything. If he ignores that then drag him before the Supreme Court. As Ackerman says, Obama is in many ways going much further than President Bush, who at least sought specific authorization to attack Iraq. It's high time the imperial presidency got put back in its box.