Testifying in front of the Senate Foreign Relations Committee Monday evening, Secretary of State Rex Tillerson and Secretary of Defense James Mattis argued that measures passed by Congress days after the Sept. 11, 2001, terror attacks and in 2002 during the run-up to the 2003 Iraq war continue to hold merit.

“This has been a long 16-year conflict characterized by a very different kind of warfare,” Mattis told the committee. “The 2001 and 2002 authorizations to use military force, or AUMF, remain a sound basis for ongoing U.S. military operations against a mutating threat.”

That “mutating threat” led Mattis and Tillerson to lay out conditions for any new use of force Congress considers. They both argued that a repeal of the existing measures “would call into question the domestic legal basis for the United States’ full range of military activities against the Taliban, Al-Qaida, and associated forces, including ISIS,” as Tillerson put it.