Just over two weeks after Rep. Barbara Lee (D-Calif.) succeeded in adding an amendment to the 2018 Defense Appropriations Bill that would have repealed the 2001 Authorization for Use of Military Force, House Speaker Paul Ryan (R-Wis.) reportedly killed the amendment late Tuesday night with no debate or discussion.

Lee took to Twitter to denounce Ryan's move as "underhanded" and "undemocratic."

"Ryan should be ashamed of himself for forcing Republicans to strip out my bipartisan AUMF amendment in the dead of night," Lee wrote. "What is he afraid of?"

Ryan stripped my 01 AUMF repeal amdt from DOD Approps in the dead of night. This is underhanded & undemocratic. The people deserve a debate! — Rep. Barbara Lee (@RepBarbaraLee) July 19, 2017

Ryan should be ashamed of himself for forcing Republicans to strip out my bipartisan AUMF amdt in the dead of night. What is he afraid of? — Rep. Barbara Lee (@RepBarbaraLee) July 19, 2017

In 2001, Lee was the only member of Congress to vote against the AUMF, which provided authorization (pdf) for the administration of George W. Bush to take military action against "those nations, organizations, or persons he determine[d] planned, authorized, committed, or aided" the September 11 attacks.

The measure has since been used expansively to authorize military actions throughout the Middle East by the Obama and Trump administrations.

Lee has for years called for the measure's repeal. Following her momentary victory last month, when Democrats and Republicans in the House Appropriations Committee voted overwhelmingly to include her AUMF repeal amendment in the 2018 Defense Appropriations Bill, Lee celebrated the step toward "put[ting] an end to the overly broad blank check for war that is the 2001 AUMF."

"Congress has been missing in action on matters of war and peace for nearly sixteen years."

—Rep. Barbara Lee"If passed into law as part of the DoD bill, it would repeal the 2001 AUMF eight months after enactment of this legislation. That would allow plenty of time for Congress to finally live up to its constitutional obligation to debate and vote on any new AUMF," Lee added. "It is far past time for Congress to do its job and for the Speaker to allow a debate and vote on this vital national security issue."

The specifics surrounding Ryan's quiet, late-night move to kill Lee's amendment are unclear.

"Getting to the bottom of this as we speak," Lee's office told Buzzfeed reporter Emma Loop Tuesday night.

In a statement on Wednesday, Lee said the effort to stifle debate on America's wars is "autocratic" and "may be a new low from Speaker Ryan."

"Congress has been missing in action on matters of war and peace for nearly sixteen years. Republican leadership showed last night that they will do anything to maintain this status quo," Lee said. "Refusing to debate and vote on our ongoing wars is an abdication of our constitutional responsibility. Our men and women in uniform deserve better."