The House of Representatives has voted overwhelmingly, 247-175, in favor of a resolution to cut off US support for the horrific Saudi-led assault on Yemen, joining the Senate in a historic reassertion of the authority of Congress to make decisions regarding wars and military interventions by the United States.

“Today is a historic day for peace,” Diane Randall, the executive director of the Friends Committee on National Legislation, which has been in the forefront of the struggle to end US support for the Saudi-led war and the de facto blockade of Yemen, declared shortly after Thursday’s vote.

For peace, yes; and also for the Congress and the Constitution.

“For the first time in American history, both the House of Representatives and the Senate have voted on—and passed—a measure to invoke the War Powers Resolution to end unauthorized US participation in a foreign conflict,” declared Congressional Progressive Caucus co-chair Mark Pocan, a Wisconsin Democrat. That resolution will now go to the desk of an imperial president who has disregarded the US Constitution, and his own oath of office, in order to steer the United States into an unauthorized and inappropriate military adventure.

Vermont Senator Bernie Sanders, who worked with Democrats (especially Chris Murphy of Connecticut) and Republicans (especially Mike Lee of Utah) to secure Senate support for the measure late last year, put Thursday’s House vote to “end the United States’ unconstitutional support for the catastrophic war in Yemen” in perspective when he identified it as “a message to Trump: It’s Congress—not the President—who has the power to declare war.”

Congressman Ro Khanna, the California Democrat who has so ardently championed the struggle to reassert congressional authority when it comes to warmaking, described the historic House vote as “the culmination of a years long, bicameral and bipartisan effort to end the world’s worst modern humanitarian crisis.”

Khanna is right, but this fight is not finished. Every indication is that President Trump will veto the measure, setting up a critical test for Congress. The House and the Senate must attempt to override a presidential veto.

Unfortunately, too many members of both parties put partisanship ahead of a Constitution that grants the Congress—not the president—the power to declare wars and authorize military interventions and partnerships. While there were a number of courageous Republicans in the House and the Senate who worked with Sanders, Khanna, Pocan, and longtime advocates for restoration of this essential check and balance on the executive branch such as Congresswoman Barbara Lee (D-CA), the votes in both chambers generally split along party lines.

Now, Congress must make an existential choice. The House and the Senate have voted “to direct the removal of United States Armed Forces from hostilities in the Republic of Yemen that have not been authorized by Congress.” No matter where a member of either chamber, and of either party, may stand on the specific question of US engagement with Saudi Arabia and the crisis in Yemen, a Trump veto would represent a rejection by a sitting president of the will of bipartisan majorities in a Republican-controlled Senate and a Democratic-controlled House on a matter of war and peace.

That sets up a definitional question for members of both chambers who have sworn oaths to “support and defend the Constitution of the United States against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same”—do they choose to preserve the separation of powers and the system of checks and balances as outlined in the Constitution, or do they choose to do the bidding of the imperial presidency?