Bob Corker, a Republican, represents Tennessee in the Senate, where he is the ranking member of the Foreign Relations Committee.

One week after the 9/11 attacks, Congress authorized the president “to use all necessary and appropriate force against those nations, organizations, or persons he determines planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001.” More than 12 years later, the president continues to rely on this 60-word authorization to fight terrorist organizations around the world. This week, the Senate Foreign Relations Committee held a hearing on this subject, the first step in an effort to reassert congressional oversight of this issue, which has fundamentally changed from the initial hunt for Osama bin Laden.

A recent State Department report revealed how the diminishment of al-Qaeda’s central leadership corresponds with the growing strength and proliferation of its affiliates and other terrorist groups, contributing to a 43 percent increase in global terrorist attacks in 2013. Today’s terrorists may invoke the brand and methods of al-Qaeda, but they have evolved in ways that suggest that our legal foundation for conducting drone strikes or raids is outdated and inadequate.

For example, al-Qaeda’s recent expulsion of the ruthless Islamic State of Iraq and the Levant from its ranks has forced the Obama administration’s lawyers to question whether, under the auspices of the 9/11 law, the president still has the authority to target that group. In other words, there are legitimate doubts about whether the president can take necessary actions against the most dangerous terrorist group in Syria in a conflict that — according to recent congressional testimony from the director of national intelligence — has attracted more than 7,000 foreign fighters from 50 countries, some with aspirations to attack the U.S. homeland. This follows the testimony of Gen. Martin Dempsey, the chairman of the Joint Chiefs of Staff, who conceded that the terrorists responsible for killing four Americans in Benghazi are not covered under the current resolution.

These incidents seem to suggest that the September 2001 Authorization on the Use of Military Force (AUMF) is too narrow and that the president is hamstrung by stale semantic distinctions. But there are also legitimate reasons to believe it is too broad. Both the Obama and Bush administrations have stretched the resolution’s authority well beyond its words to go after groups that have little to no connection to the attacks on the World Trade Center and the Pentagon.

Aware of these problems, the Obama administration has hinted that the 9/11 AUMF might expire, at least in part, once combat operations ease in Afghanistan and the president draws down U.S. forces. Yet the administration has offered no legal justification for how important counterterrorism operations could then continue in places such as Somalia and Yemen — nor has it explained what would happen to enemy combatants held at Guantanamo Bay, Cuba.

Given the complexity and importance of these issues, I welcomed President Obama’s May 2013 speech in which he aptly pointed out that “the threat has shifted and evolved from the one that came to our shores on 9/11” and pledged to work with Congress on revising the 12-year-old resolution.

Unfortunately, the president has since failed to engage Congress on the issue.

Two of his top lawyers went before the Senate this week and said they had been cleared to discuss the issue with senators but then refused to do so. The administration’s witnesses could not say whether the president acknowledges any limits on his executive power to use force without congressional authority, and they refused to identify which groups are and are not covered by the 2001 law. Instead, they offered some support for repealing the 2002 Iraq AUMF. However, this doesn’t address the more important challenges facing us in the evolving conflict against al-Qaeda and other terrorist groups.

An issue this critical to U.S. national security demands a robust debate to ensure that counterterrorism efforts reflect American values and laws, while respecting the president’s authority and preserving the flexibility to employ covert action in appropriate circumstances. The existing authority should be both narrowed and broadened — to create a mechanism for regular congressional oversight and reporting from the administration, including a possible sunset date to revisit the law, and to allow for the addition of organizations that were not involved in 9/11 but nonetheless pose a direct threat to the United States and our interests.

Absent congressional action, the president will continue to operate under an outdated authorization, leaving the door open for future presidents to claim undue and unbounded powers that will, over time, erode the balance of power fundamental to our constitutional system.

Terrorist groups with global reach will continue to present a serious threat for the foreseeable future. Rather than abdicating the responsibility for confronting them and leaving it to the executive branch — as it has done too often — Congress should take advantage of this unique opportunity to act in a bipartisan fashion.