At a Wednesday press conference, Senators Bernie Sanders (I-VT) and Mike Lee (R-UT) unveiled the bipartisan Senate resolution which aims to force an end to the US military involvement in the Saudi-led invasion of Yemen.

The bill makes use of the 1973 War Powers Act, which allows any legislator to introduce a resolution which would compel a withdrawal from any conflict that was not specifically authorized by Congress in any Authorization for the Use of Military Force (AUMF). Neither of the two extent AUMFs have anything to do with the attack on Yemen’s Shi’ite Houthi movement.

This is the first time the Senate will have ever made a War Powers challenge to a conflict. A previous effort at such a legal challenge in the House was derailed by the leadership, and replaced with a “non-binding” resolution noting the Yemen war was unauthorized, which overwhelmingly passed.

Both Sanders and Lee made clear the opposition was not a partisan issue, since US involvement in the war started under President Obama and continued under President Trump. The Senate leadership have not indicated what they intend to do about the challenge yet.

Centcom commander Gen. Joseph Votel confirmed to the House Armed Services committee only the day prior that the US does not have an AUMF for Yemen, and that America’s involvement is solely a function of having sold the arms to the Saudis in the first place, and promising to “provide support” for those arms.

Yet legally, Congress is supposed to have the war-making powers, and this Senate effort stands to be the first time in recent history that Congress looks like they might be reasserting that authority.