Citing a raging humanitarian crisis as well as constitutional law, more than three dozen legal scholars, human rights advocates, and former officials urged the U.S. Senate on Thursday to back a proposal that would end U.S. involvement in the war in Yemen.

Yale Law School professor Bruce Ackerman, Nobel Peace Laureates Jody Williams and Tawakkol Karman, and former U.S. ambassador Stephen Seche were among the experts who sent a letter to every senator asking them to support a resolution proposed by Sens. Bernie Sanders (I-Vt.), Chris Murphy (D-Conn.), and Mike Lee (R-Utah) to remove U.S. forces from the conflict in Yemen, as no military action there has been authorized by Congress.

"We strongly encourage you and your Senate colleagues to co-sponsor and vote for S.J. Res 54, which defends the constitutional linchpin of Congress's sole authority to declare war and promises to help end what aid groups consider the worst humanitarian crisis in the world," the letter stated.

"For far too long, Congress under Democratic and Republican administrations has abdicated its constitutional role in authorizing war."—Sen. Bernie Sanders (I-Vt.)

The Saudi-led coalition, which has backed Yemen's government forces in their fight against the Houthi rebels since 2015, has been provided with weapons, refueling support, and intelligence by the U.S. as well as the U.K. and France.

The war has plunged Yemen, already one of the poorest countries in the Middle East, into a grave humanitarian crisis, with 8.4 million people living on the brink of famine.

Under the bipartisan resolution proposed last week, the Senate would direct "the removal of U.S. forces from such unauthorized hostilities within 30 days unless and until a declaration of war or a specific statutory authorization is enacted," wrote the experts.

As Mark Weisbrot of the Center for Economic and Policy Research wrote in a column this week, the letter is "historic in that it invokes the 1973 War Powers Resolution, which was legislated toward the conclusion of a long struggle to end U.S. military involvement in Vietnam. The law requires that Congress must have a debate and vote on ending involvement of U.S. military forces in unauthorized hostilities, if a member of Congress requests it."

"The founding fathers gave the power to declare war to Congress, the branch most accountable to the people," said Sanders last week when he introduced the proposal. "For far too long, Congress under Democratic and Republican administrations has abdicated its constitutional role in authorizing war."