In previous posts, I addressed some of the most common arguments justifying President Obama’s decision to launch a large-scale military campaign against ISIS without getting any new authorization from Congress.

Over the last few days, defenders of the President’s position have advanced some new arguments, as well as refinements of the old ones. In this post, cover the most important of these. Some of them are much better than the administration’s own reliance on the 2001 AUMF. But none actually work.

I. Defense Against Attack.

Perhaps the strongest of the newer arguments for Obama’s decision is Michael Ramsey’s theory that he does not need congressional authorization because he is merely responding to the intiation of war by ISIS, including a seeming declaration of war against the US by that organization.

Most experts agree that the president does not need congressional authorization to fight war in response to an attack by external enemies. And, as the war with al Qaeda demonstrates, the enemy in question need not be a state actor. Ramsey is also correct to argue that the president can wage war against a foreign power in response to a declaration of war against the United States by that country – even if the nation in question has not yet launched an actual military attack against the US large enough to qualify as a war under other circumstances.

The self-defense theory has several virtues. It does not rely on a strained interpretation of the 2001 Authorization for the Use of Military Force, or the 2002 Iraq AUMF. And unlike John Yoo’s theory of executive war powers, it does not give the president blanket authority to initiate new wars on his own.

But the idea nonetheless has some real flaws. ISIS’ atrocities in beheading two American journalists and holding a few other Americans hostage are horrendous. But it’s hard to argue they are an attack against the US on a large enough scale to count as a war. Serial murderers such as Ted Bundy and the Unabomber probably killed as many or more Americans than ISIS did before Obama ordered air strikes against it (like ISIS, the Unabomber even did it for political reasons). The same is true of quite a few pre-9/11 foreign terrorists. Yet few claim that their actions amount to initiating a war against the United States.

As for ISIS’ declaration of war, it might indeed be enough to give the president authority to wage war in response if issued by an internationally recognized state. But issued by a mere terrorist organization, it does not rise to the same level. Otherwise, the president would have the authority to launch a full-scale war without congressional authorization any time some small group of crazies issue a statement claiming that they are at war with the US. The president might have the authority to wage war against it if the group launched a large scale attack comparable to 9/11 or was imminently threatening to do so. But a terrorist group cannot trigger that power merely by issuing a statement or killing a very small number of people. The president can use law enforcement measures and small-scale military attacks in such cases, but not initiate a full-scale war without congressional authorization.

II. Continuity Between ISIS and al Qaeda.

Famed Harvard law professor (and former Obama administration official) Cass Sunstein argues that Obama’s air strikes are authorized by the 2001 AUMF against the perpetrators of the 9/11 attacks. The 2001 AUMF is limited to “those nations, organizations, or persons [the president] determines planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001, or harbored such organizations or persons.”
An organization that did not even exist in 2001 and is currently an enemy of al Qaeda’s seems to fall outside that definition. Moreover, as Bruce Ackerman points out, the 2001 AUMF was deliberately drafted more narrowly than the Bush administration wanted, in order to deny the president the power to wage an open-ended war against any and all potentially threatening terrorists. But, Sunstein argues that ISIS is nonetheless close enough to al Qaeda to come within the scope of the 2001 AUMF:

No one doubts that the AUMF authorizes the president to fight people who have joined al-Qaeda. It’s also clear that the president can use force against any group that links itself to al-Qaeda, at least if it can be considered part of the same “organization…..”

In light of Islamic State’s close working relationship with al-Qaeda, the president could “determine” that it was essentially part of the group in 2004 and for a significant period thereafter. Indeed, Islamic State has often been described as “al-Qaeda in Iraq,” and it has reportedly been subject to al-Qaeda’s direction and control.

Last February, however, al-Qaeda publicly dissociated itself from Islamic State, partly because of Islamic State’s brutality, including beheadings. So now the question is: Does this mean that Islamic State can no longer be treated as part of an “organization” responsible for the attacks of 9/11, such that the president cannot act (in the words of the AUMF) “to prevent any future acts of international terrorism against the United States”?

Skeptics may think so, but it’s hard to see why. Imagine that in 2012, al-Qaeda split into two organizations: the original one and a new, more brutal group with a new name. Under the AUMF, the president would plainly have the authority to use force against both.

True, the Islamic State situation is not precisely the same, because it has always had its own name and identity. But if it was part of al-Qaeda for a significant period, it’s not easy to argue that al-Qaeda’s announcement of dissociation last February (for excessive brutality, no less) suddenly deprives the president of the authority he had in January. Keep in mind that the group insists it is the true inheritor of the legacy of Osama bin Laden.

If ISIS really were just a part of al Qaeda that later broke off, Sunstein’s analysis would be correct. But, as he recognizes, it has always had its own name and identity, and relations between the two groups had always been tense, even before their official break in February.

Using the 2001 AUMF to attack a separate group that had previously aided AQ and had a loose affiliation with it, but is now an enemy, seems a huge stretch. By that standard, FDR or Truman could have used the declaration of war against Nazi Germany to attack Franco’s Spain in 1945. After all, Franco’s regime and Hitler’s had similar ideologies, and had been allies in the past. German and Italian troops helped Franco win the Spanish Civil War, and Franco returned the favor by sending troops to aid the German war effort during World War II. The fact that he withdrew his troops in 1943 and later broke with Hitler would not have mattered any more than al Qaeda’s break with ISIS matters.

In a world where there are often connections between different nations and terrorist groups that are hostile to the US, Sunstein’s theory amounts to a rule that authorizing war against any one of them means authorizing a war against all of them. It may sometimes be good policy to start wars with the ideological soulmates and former friends of our enemies. But such action requires congressional authorization. That is not only the best legal standard, but also a valuable safeguard against potential presidential overreaching.

In this case, I think President Obama is right to target ISIS. But his actions are a dangerous precedent for the future. In general, it is best to have a broad consensus before embarking on war. The constitutional requirement of congressional authorization helps ensure that.