The Rotunda of the U.S. Capitol is seen behind a statue of George Washington as Congress leaves Washington for a week, Friday, March 15, 2019. (AP Photo/J. Scott Applewhite)

The Senate rightfully rediscovered its constitutional authority this week with two votes opposing President Donald’s Trump’s assertion of executive power to use military forces without congressional authorization and to declare a national emergency on the Mexican border. While there are compelling arguments on both sides of each question, the move to re-establish Congress’ proper authority was good for that body and the nation.

On Wednesday the Senate voted, 54-46, to give the president 30 days to remove all U.S. military personnel now assisting the Saudi Arabian government and its allies in their conflict with the Houthi rebels in Yemen. If the resolution also passes the House — a good bet — it will mark the first time Congress has invoked its power to cancel military operations under the 1973 War Powers Resolution.

Six Republican senators joined all the Democrats in voting for the resolution.

The argument for the measure cited by its sponsor, Republican Sen. Mike Lee of Utah, is that Congress never authorized the deployment of U.S. military personnel and equipment to assist the Saudi coalition and that, whatever the merits of their task, it is unconstitutional.

The countering argument advanced by a number of senators was that the resolution missed its target because the American forces are allegedly not engaged in hostilities as defined in the War Powers Resolution, but are helping the Saudi coalition minimize civilian casualties by providing precise targeting intelligence for offensive operations, protecting Saudi civilians from missile attacks and other non-combat assistance.

Withdrawing the forces, including those providing aerial refueling outside the combat area to Saudi warplanes, could lead to more indiscriminate targeting of Yemeni civilians and leave Saudi civilians at the mercy of missile attacks, they said.

Senate Majority Leader Mitch McConnell, R-Ky., asked senators to vote against the resolution and said it was an inappropriate way to record dissatisfaction with the government of Saudi Arabia. But it is notable that he allowed the measure to come to a vote without invoking a filibuster.

It is unclear what the result will be of invoking the War Powers Resolution. Every president since Richard Nixon has declared it an unconstitutional infringement of presidential powers involving a legislative veto not recognized in the Constitution. If the House goes along with the Senate, the issue is very likely headed to the courts.

On the other hand, Thursday’s adoption of a resolution of disapproval overturning Mr. Trump’s declaration of a national emergency on the southern border faces an even less certain future. The presidential declaration offended nearly a quarter of the Senate’s 52 Republicans, but their 12 votes in the 59-41 decision are not enough for a veto-proof majority.

As expected, Mr. Trump vetoed the measure on Friday, which could also leave the resolution of the legitimacy of his emergency declaration up to the federal courts.

Interestingly, Mr. Trump had tweeted that he would support a move by Senate Republicans to update the law granting him emergency powers. Mr. Trump had hoped his support for the idea would persuade senators to vote against the resolution of disapproval, but the only one who changed his mind because of the president’s promise was Thom Tillis, R-N.C.

As Sen. Tillis said Thursday, the idea that the president would give back to Congress some of the powers it had granted him is unusual in the history of executive-congressional relations. The idea is a good one and should be pursued.