The Authorization for Use of Military Force, a joint resolution passed by Congress three days after the strikes on the World Trade Center and the Pentagon, has served as the legal foundation for U.S. counterterrorism operations against al-Qaida over the past decade, including ongoing drone campaigns in Pakistan and Yemen that have killed thousands of people.
But U.S. officials said administration lawyers are increasingly concerned that the law is being stretched to its legal breaking point, just as new threats are emerging in countries including Syria, Libya and Mali.
"The farther we get away from 9/11 and what this legislation was initially focused upon," a senior Obama administration official said, "we can see from both a theoretical but also a practical standpoint that groups that have arisen or morphed become more difficult to fit in."
The waning relevance of the 2001 law, the official said, is "requiring a whole policy and legal look." The official, like most others interviewed for this article, spoke on the condition of anonymity to discuss internal administration deliberations.
The authorization law has already been expanded by federal courts beyond its original scope to apply to "associated forces" of al-Qaida. But officials said legal advisers at the White House, the State Department, the Pentagon and intelligence agencies are now weighing whether the law can be stretched to cover what one former official called "associates of associates."
The debate has been driven by the emergence of groups in North Africa and the Middle East that may embrace aspects of al-Qaida's agenda but have no meaningful ties to its crumbling leadership base in Pakistan. Among them are the al-Nusra Front in Syria and Ansar al-Sharia, which was linked to the September attack on a U.S. diplomatic post in Benghazi, Libya. They could be exposed to drone strikes and kill-or-capture missions involving U.S. troops.
Officials said they have not ruled out seeking an updated authorization from Congress or relying on the president's constitutional powers to protect the country. But they said those are unappealing alternatives.
The debate comes as the administration seeks to turn counterterrorism policies adopted as emergency measures after the 2001 attacks into more permanent procedures that can sustain the campaign against al-Qaida and its affiliates, as well as other current and future threats.
The AUMF, as the 2001 measure is known, has been so central to U.S. efforts that counterterrorism officials said deliberations over whom to put on the list for drone strikes routinely start with the question of whether a proposed target is "AUMF-able."
The outcome of the debate could determine when and how the war on terrorism - at least as defined by Congress after the Sept. 11 attacks - comes to a close.
"You can't end the war if you keep adding people to the enemy who are not actually part of the original enemy," said a person who participated in the administration's deliberations on the issue.
Administration officials acknowledged that they could be forced to seek new legal cover if the president decides that strikes are necessary against nascent groups that don't have direct al-Qaida links. Some outside legal experts said that step is all but inevitable because the authorization has already been stretched to the limit of its intended scope.
"The AUMF is becoming increasingly obsolete because the groups that are threatening us are harder and harder to tie to the original A.Q. organization," said Jack Goldsmith, an expert on national security law at Harvard University and a former senior Justice Department official.
He said extending the AUMF to groups more loosely tied to al-Qaida would be "a major interpretive leap" that could eliminate the need for a link between the targeted organization and core al-Qaida.
The United States has not launched strikes against any of the new groups, and U.S. officials have not indicated that there is any immediate plan to do so. In Libya, for example, the United States has sought to work with the new government to apprehend suspects in the Benghazi attack.
Still, the administration has taken recent steps - including building a drone base in the African country of Niger -- that have moved the United States closer to being able to launch lethal strikes if regional allies are unable to contain emerging threats.
The administration official cited Ansar al-Sharia as an example of the "conundrum" that counterterrorism officials face.
The group has little if any established connection to al-Qaida's leadership core in Pakistan. But intercepted communications during and after the attack in Benghazi indicated that some members have ties to al-Qaida in the Islamic Maghreb, the terrorist network's main associate in North Africa.
"Certainly there are individuals who have an affiliation from a policy, if not legal, perspective," the official said. "But does that mean the whole group?"
Other groups of concern include the al-Nusra Front, which is backed by al-Qaida in Iraq and has used suicide bombings to emerge as a potent force in the Syrian civil war, and a splinter group in North Africa that carried out a deadly assault in January on a natural-gas complex in Algeria.
The debate centers on a piece of legislation that spans a single page and was drafted in a few days to give President George W. Bush authority to "use all necessary and appropriate force" against al-Qaida.
The law placed no geographic limits on that power but did not envision a drawn-out conflict that would eventually encompass groups with no ties to the Sept. 11 strikes. Instead, it authorized the president to take action "against those nations, organizations, or persons he determines planned, authorized, committed, or aided the terrorist attacks."
The authorization makes no mention of "associated forces," a term that emerged only in subsequent interpretations of the text. But even that elastic phrase has become increasingly difficult to employ.
In a speech last year at Yale University, Jeh Johnson, who served as general counsel at the Defense Department during President Barack Obama's first term, outlined the limits of the AUMF.
"An 'associated force' is not any terrorist group in the world that merely embraces the al-Qaida ideology," Johnson said. Instead, it has to be both "an organized, armed group that has entered the fight alongside al-Qaida" and a "co-belligerent with al-Qaida in hostilities against the United States or its coalition partners."
U.S. officials said evaluating whether a proposed target is eligible under the AUMF is only one step. Names aren't added to kill or capture lists, officials said, unless they also meet more elaborate policy criteria set by Obama.
If a proposed a target doesn't clear the legal hurdle, the senior administration official said, one option is to collect additional intelligence to try to meet the threshhold.
Officials stressed that the stakes of the debate go beyond the drone program. The same authorities are required for capture operations, which have been far less frequent. The AUMF is also the legal basis for the CIA's drone campaign in Pakistan, although the agency compiles its own kill list in that operation with little involvement from other agencies.
The uncertainty surrounding the AUMF has already shaped the U.S. response to problems in North Africa and the Middle East. Counterterrorism officials concluded last year that Mokhtar Belmokhtar, a militant leader in Algeria and Mali, could not be targeted under the AUMF, in part because he had had a falling out with al-Qaida's leadership and was no longer regarded as part of an associated group.
Belmokhtar was later identified as the orchestrator of the gas-plant attack in Algeria in which dozens of workers, including three Americans, were killed.
Obama's decision to provide limited assistance to French air attacks against Islamist militants in Mali this year was delayed for weeks, officials said, amid questions over whether doing so would require compliance with the AUMF rules.
Some options beyond the 2001 authorization are problematic for Obama. For instance, he has been reluctant to rely on his constitutional authority to use military force to protect the country, which bypasses Congress and might expose him to criticism for abuse of executive power.
Working with Congress to update the AUMF is another option. The Senate Intelligence Committee has already begun considering ways to accomplish that. But Obama, who has claimed credit for winding down two wars, is seen as reluctant to have the legislative expansion of another be added to his legacy.
"This is an ongoing discussion, which we'll probably continue to engage on the Hill," the senior administration official said. "But I don't know that there's a giant desire to have 'Son of AUMF' now."
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