Although the president thinks such constitutional niceties are unnecessary, Congress may vote on a resolution authorizing his campaign against the Islamic State in Iraq and Syria. While many lawmakers are content to have the chief executive assume all the political risk, there is bipartisan support for the idea.

I’m not one of those conservatives who thinks an authorization of force is somehow constitutionally inferior to a formal declaration of war. While there are advantages to the latter, the important principle is that hostilities are only initiated after Congress votes.

But authorization of force resolutions can be abused, especially when they are crafted in an open-ended way. Consider the arguments for why President Obama can go to war without congressional approval. Only some of them rely on defining Congress’s power to declare war down or an outsized view of executive power.

More commonly, we hear that preexisting authorizations of force apply to the current situation, even though conditions are obviously very different than when those resolutions were originally enacted.

The Obama administration apparently believes it has the legal justification to attack ISIS under the resolution that authorized the war on terror in 2001. But that law quite specifically covers “those nations, organizations, or persons” that “planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001, or harbored such organizations or persons.”

“On its face this is an implausible argument because the 2001 AUMF requires a nexus to al Qaeda or associated forces of al Qaeda fighting the United States,” Robert Chesney, a professor at the University of Texas School of Law, told The Daily Beast. “Since ISIS broke up with al Qaeda it’s hard to make that argument.”

Even the Bush administration accepted that it needed a separate authorization of force to go to war in Iraq, even though some of its officials and defenders were asserting a connection between 9/11 and Saddam Hussein’s regime. Meanwhile, President Obama is winding down the war most directly associated with the 2001 law: Afghanistan.

Others think the 2002 authorization of military force that allowed the war in Iraq would do the trick. This somewhat surprisingly includes the White House, since Obama opposed its passage (though he was not yet in the Senate to vote on it at the time) and the administration not long ago went on record in favor of its repeal.

“With American combat troops having completed their withdrawal from Iraq on December 18, 2011, the Iraq AUMF is no longer used for any U.S. government activities and the Administration fully supports its repeal,” Obama National Security Adviser Susan Rice wrote to Congress in July.

At the time, Rice seemed to hope that repeal would reassure the American people “that ground forces will not be sent into combat in Iraq” as the administration returned to fight ISIS. Bizarrely, she seemed to be floating repeal of the Iraq war authorization as an alternative to Congress authorizing a new Iraq intervention.

July was a long time ago in Washington. The administration has since told the New York Times “the 2002 Iraq A.U.M.F. would serve as an alternative statutory authority basis on which the president may rely for military action in Iraq.” The unnamed official quoted in the story added somewhat incoherently, “Even so, our position on the 2002 A.U.M.F. hasn’t changed and we’d like to see it repealed.”

This muddiness actually undermines any legal claim the Iraq authorization covers military action against ISIS. This would have to be a resumption of the old war (which the administration is trying to deny) rather than the beginning of a new one (which the administration is also trying to deny).

In any event, Congress based its 2002 vote in favor of the Iraq War on the (wildly exaggerated) threat of Saddam’s weapons program. It is hard to imagine they thought they were authorizing another war more than a decade later after Saddam was gone and the weapons of mass destruction were never found.

Nevertheless, some of us warned that if the Iraq authorization wasn’t repealed it would be used as the basis for another war.

Unfortunately, none of these machinations are new. When George W. Bush contemplated his Iraq invasion, some argued that he needed no congressional authorization. Either the post-9/11 resolution or the authorization for the Persian Gulf War waged under his father over a decade prior would cover it.

The 2001 war on terror authorization perhaps gave presidents more discretion than originally envisioned and some legislation being considered would be even broader.

It goes to show that in order to protect its constitutional war powers and restrain the president’s—to say nothing of avoiding unanticipated perpetual war—Congress must do more than pass generous authorizations of military force.

W. James Antle III is editor of the Daily Caller News Foundation and author of Devouring Freedom: Can Big Government Ever Be Stopped?