For years now, the questions of where and with whom exactly the United States is at war have been treated as somewhat academic. It’s not that they didn’t matter, but a gridlocked Congress seemed unwilling or unable to take the issue on or to pass a law clarifying the Obama administration’s authority to use force in any meaningful way. The administration, for its part, seemed happy to leave the edges of its authority fuzzy, claiming the 2001 Authorization for Use of Military Force passed after 9/11 covered the bulk of its military actions, without getting too specific.

As Charlie Savage points out in The New York Times, however, last week’s US airstrike in Somalia that killed 150 suspected al-Shabaab fighters highlights some serious questions raised by leaving the scope of this ongoing 15-year war so unclear. And it signals, as University of Texas law professor Robert Chesney points out, the US legal rationale for striking al-Shabaab can be interpreted so broadly as to have virtually no limit. If Congress doesn’t act to change that before the end of his term, President Obama will be leaving that open-ended authority to the next president — whoever he or she may be.

The Obama administration over the years has justified its broad interpretation of war authority in various ways, depending on the situation. This time, a Pentagon spokesman told Savage that although the government has not deemed al-Shabaab to be an “associated force” in the war against al-Qaeda, the strike was nevertheless “authorized by the 2001 A.U.M.F.” — as were three previous strikes in Somalia last year. The strikes were covered, the Pentagon claims, because the United States has ground troops in Somalia advising Amisom — the African Union’s peacekeeping force there — and those troops faced a “continuing and imminent” threat from al-Shabaab fighters. The US sent those advisors both to help stabilize Somalia against al-Shabaab generally, and to help fight those within al-Shabaab who are believed to be affiliated with al-Qaeda. That al-Qaeda connection, even if secondary, brings it all under the AUMF’s authority, or so the administration’s theory goes.

Chesney has appropriately questioned whether the administration is following the use-of-force policy it announced in 2013. This policy — which covers “operations to capture or employ lethal force against terrorist targets outside the United States and outside areas of active hostilities” — is based on the administration’s Presidential Policy Guidance. (The government recently announced that it will release the Guidance for the first time (with redactions) in connection with FOIA litigation brought by the ACLU.) But as Chesney told Savage, the airstrike in Somalia also raises a larger question of whether there are any meaningful limits in the Pentagon’s model for the use of force anywhere the US has stationed troops in any sort of role. As Chesney put it: “According to this logic, if you have got a ‘continuing and imminent threat’ to those advisers, it sounds like you have a really broad aperture for pre-emptively attacking the threat.”

If Congress remains unable to agree on how to define the president’s war authority, it will be up to President Obama to spell out a clear and well-reasoned explanation of the scope of our current wars for his successor.

That explanation should include:

  1. a more precise — and public — explanation of whom the US is at war with, including more clearly defining what is meant by “associated forces”;
  2. when the United States is using force pursuant to the 2001 AUMF, as opposed to when its use of force outside a zone of active hostilities is in “self-defense”;
  3. what counts as an “imminent threat” and how a threat can logically be both “continuing” and “imminent”;
  4. which “international law principles” the administration adheres to and how it defines them;
  5. how the United States will determine the “cessation of hostilities,” for purposes of ending indefinite detention, in a war where the enemy is defined as constantly changing and the conflict therefore appears endless; and
  6. what circumstances would make the use of military commissions appropriate, when the administration has repeatedly acknowledged that Article III federal courts have been far more effective at safely prosecuting individuals on terrorism-related charges, while also helping law enforcement gather valuable intelligence and prevent future attacks.

While much of the media focuses on the latest outrageous statements made in the presidential campaign or who stands where in the horse race, President Obama needs to carefully consider the consequences of handing over the Oval Office without clarifying how the United States defines the scope of its armed conflicts.

Setting forth the contours of this 15-year war would help explain to the American people — and to the rest of the world — how domestic and international law and wise, carefully-considered policies guide the United States’ use of force. It would also help ensure that those considerations continue to guide US military action in the future.