Democratic Senator Tim Kaine of Virginia recently called the ongoing war against ISIS “illegal” because it lacks congressional authorization:

Sen. Tim Kaine said Wednesday there’s no legal authority for the current U.S. mission against ISIS in Iraq and Syria.

“We have been engaged in a war — that is not about imminent defense of the United States — without legal authority,” the Virginia Democrat said at the Wilson Center on Wednesday…

The mission is not covered by either the wording or intent of the 2001 and 2002 authorizations for use of military force as the White House argues, Kaine said, adding that such an argument is “ridiculous” and inconsistent with President Barack Obama’s previously stated interpretation of the AUMF.

Kaine, a member of the Senate Foreign Relations Committee, has proposed a new, limited authorization, specifically targeted to the current mission against ISIS. “We should deal with it right away,” he said, stressing that it could be accomplished in the lame-duck session in Congress.

I think Kaine is absolutely right about this. In previous posts, I explained why the operation against ISIS requires new congressional authorization and was not authorized by either post-9/11 2001 Authorization for the Use of Military Force or the 2002 AUMF (see here and here).

I also think that Kaine is right to call on Congress to address this issue sooner rather than later. Among other things, it has become more urgent thanks to President Obama’s recent dispatch of 1500 more troops to Iraq.

Like Kaine, I also believe there may well be good justification for using force against ISIS in order to keep it from becoming more powerful, protect vulnerable civilians, and hopefully reverse the gains the terrorist group has already made. But Kaine is right to emphasize that a large-scale military operation like this one requires “a political consensus” behind it. A congressional resolution endorsing the mission and clearly delineating its scope could help achieve that goal. If there is not enough support for such a resolution to pass, that suggests we do not really have the political will to see the mission through, and should cut our losses while we still can. Even aside from constitutional issues, it is unwise to enter a potentially difficult war without broad political support. Such a policy risks a quick collapse of will as soon as any setbacks occur. And fighting and losing is often both more costly and more dangerous than not fighting at all would have been.

Kaine previously outlined his position on the need for congressional authorization here. He deserves credit for being willing to stand up to a president of his own party on this issue. Kaine’s stance on the legality of the war is similar to that outlined by GOP Senator Rand Paul. But, obviously, it is much easier to attack a president of the rival party than the leader of your own.