It is not that much of a stretch to say that Congress’s 2001 Authorization for Use of Military Force (AUMF) provides a legal basis for the U.S. shootdown of a Syrian jet, despite what you may read and see elsewhere. At least that proposition holds true if you assume or accept that the 2001 AUMF covers military operations to defeat ISIS. The same would apply to U.S. shootdowns of Iranian-made drones and airstrikes against Iranian-directed forces. That is, if those foreign forces pose imminent threats to U.S. or coalition forces fighting ISIS, Congress’s 2001 authorization may be said to cover the U.S. military’s use of force in self-defense.

Let me put a couple cards on the table: In writing, I have registered strong disagreement with the notion that the 2001 AUMF can be interpreted to apply to ISIS. And, as a policy, matter I have grave concerns that some White House officials are reportedly eyeing these incidents as an opportunity to get further involved in the Syrian Civil War by undercutting Assad and as an opportunity to take the fight to Iran (see reports by Just Security/Foreign Policy and in a more recent story in the Washington Post). The goals of those officials appear to exceed the narrow self-defense justification that I am outlining here.

The Pentagon has stated that the basis for these strikes against Syrian and pro-regime forces were in self-defense and legally justified under the 2001 AUMF. (See also remarks by Chairman of the Joint Chiefs of Staff Gen. Joseph F. Dunford before the National Press Club on Monday.)

On Tuesday, some Senators registered disagreement with this legal theory. One of the witnesses, former State Department Legal Advisor John Bellinger testified that he too was “puzzled about the statements coming out of the Pentagon that the shootdown was authorized by the 2001 AUMF, and I hope that they will clarify that.” In closing out the hearing, Chairman of the Senate Foreign Relations Committee, Sen. Bob Corker said, “On behalf of the committee today we’ll ask, formally, what authority they’re relying upon for this and it’ll go out today.” The Committee has now formally requested the administration’s legal justification.

So what’s the puzzle?

During the hearing, Bellinger said, “I don’t really see how it can be justified under the 2001 AUMF because Syria’s not one of the nations that committed the 9/11 attacks and it’s not a co-belligerent with Al-Qaida.” On this point, the other witness, Kathleen Hicks, senior vice president of the Center for Strategic and International Studies, followed up by saying, “I agree with everything Mr. Bellinger said.” Bellinger highlighted this aspect of his remarks in a post at Lawfare. Another post at Lawfare by professor Bobby Chesney also tries to grapple with the possible legal justification and appears to settle on a notion that the President could claim Article II authority—a space the administration need not wander if the AUMF suffices.

But Bellinger at least is looking under the wrong tree. It is not a question of whether Syria (or Iran) is linked to the 9/11 attacks or is a co-belligerent of one of the forces against with the U.S. military is authorized to conduct military operations.

So where to look to answer the puzzle?

If we assume the counter-ISIS fight is authorized by the AUMF (as mentioned that’s a big if for me, but if), then force protection of our counter-ISIL operations would be too. Imagine, for example, it wasn’t a Syrian jet but some rogue militia group that started attacking the coalition forces as they advanced on an ISIS position. Would one say Congress authorized the aggressive operation against ISIS but not self-defense on behalf of the coalition forces? Admittedly, it is more of a legal jump in a situation when only partner forces come under fire rather than when American forces are threatened too. But none of this is as “puzzling” or stretchy as others suggest.

Similar to this line of thinking, professor Monica Hakimi wrote at Just Security back in May:

“if the AUMF authorizes the fight against ISIS, then extending it to operations that are designed to protect ISIS-fighting forces does not seem like such a stretch. In other words, the administration might invoke the AUMF to justify operations against Syria, if such operations are necessary to protect our forces in the field.”

Hakimi added: “That potential application of the AUMF betrays just how far down the slippery slope we have fallen”—but that (perhaps policy-based) concern did not detract from her recognizing the legal interpretation “does not seem like such a stretch.”

While we are discussing statutory authority, it is worth drawing attention to the law that Congress passed for the U.S. to train and equip partner forces fighting ISIS in Syria. In that legislation, Congress provided that “the Secretary of Defense is authorized” to use the program “for the following purposes: Defending the Syrian people from attacks by the Islamic State of Iraq and the Levant (ISIL), and securing territory controlled by the Syrian opposition” (emphasis added). It is notable that the trained and equipped Syrian Democratic Forces were reportedly the very forces that the US strikes were defending from the Syrian jet. Nonetheless, the authorized “purpose” in that particular legislation is to be achieved through the mechanism of training and equipping, and not through U.S. use of force such as direct military strikes.  It would therefore not provide the basis for the White House officials who wish to expand the scope of U.S. military operations into a more offensive posture against Syria, Iran, and their proxies.

Finally, it is worth noting a perennial problem in this legal space. If one does not accept the theory that the 2001 AUMF covers these operations, many will turn to the President’s constitutional authority under Article II as the legal basis. If the set of choices is so limited, which stretchiness would you prefer? One that stretches the statutory interpretation under the 2001 AUMF or one that stretches the interpretation of the President’s stand-alone constitutional authority to act without congressional approval?

Image: Su-22 jet at the Syrian Air Force base in Homs province

[Editor’s note: for a timeline of escalation in Syria, between the U.S. and Iran, Russia, Syria and “pro-regime” forces see here]