The Senate Armed Services Committee on Thursday easily passed a waiver to allow retired Gen. James Mattis to serve as Defense secretary despite only leaving the military in 2013.
Current law says Pentagon chiefs must be out of uniform for at least seven years. The law has been waived just once, for George Marshall in 1950.
The committee voted immediately after Mattis's confirmation hearing earlier Thursday, in which he sought to make clear he understands the difference between civilian leadership and military service.
"I recognize my potential civilian role differs in essence and in substance from my former role in uniform," he said. "Civilian control of the military is a fundamental tenet of the American military tradition."
Gillibrand has been vocal about her opposition to the waiver since Mattis's nomination was announced, but neither Blumenthal nor Warren had explicitly said they would vote against the waiver.
Sen. Jack Reed (D-R.I.), ranking member of the committee, expressed concern about giving Mattis the exception, but said his testimony Thursday and his general character convinced him to vote for it. Still, Reed said he won't support a similar waiver for any future nominees.
The waiver now goes to the Senate floor for a the full chamber's vote.