The White House called the vote “unnecessary and unhelpful,” but it has only itself to blame. The administration faces bipartisan opposition in Congress because it has, for more than two months, sidestepped the clear constitutional and legislative intent that a president obtain congressional authorization to go to war.

At the time that President Obama was seeking endorsement for military action at the United Nations, he didn’t seek a congressional declaration of war, as specified in Article I of the Constitution. After the fighting began and U.S. planes and missiles had attacked Libyan targets, the president still declined to seek congressional approval.

The president promised that he would act consistent with the War Powers Resolution, which requires congressional approval to continue military action beyond 60 days after it commences, and to consult closely with Congress. These commitments have gone unfulfilled. The administration even barred Defense Department officials from testifying at a public hearing and canceled a private briefing for senators by a Marine general. This disdain for Congress and constitutional principles led to Friday’s nonbinding House resolution.

Belatedly, the president and his allies are trying to establish congressional endorsement for the war through a nonbinding Senate resolution approving “the limited use of military force by the United States in Libya.” But this illustration of the president’s go-it-alone attitude would set a dangerous precedent.

These “sense of the Senate” resolutions are most often used to commemorate non-controversial events such as last month’s resolution celebrating National Train Day — not to authorize a war. The resolution would have no force of law and would not have to be passed by the House. Nonetheless, it would be touted by the administration as evidence of congressional approval for the war.

Passing this resolution would be a profound mistake that would lower the standard for congressional authorization for the use of military force and would forfeit the Senate’s own constitutional role. By setting this precedent in the interests of expediency, Congress would make it far more likely that future presidents will deem a nonbinding vote in one house as sufficient to initiate or continue a war, or marginalize Congress’s involvement in far more consequential war-making decisions than we face now in Libya.

Further, because the president has not made his case to Congress, the American people have no clear understanding of the U.S. interests at stake in Libya, how much this will cost and what other priorities will have to be sacrificed.

Even the goals of the conflict remain unclear. The United Nations sanctioned only protection of civilians, and in March the president said, “Broadening our military mission to include regime change would be a mistake.” But at the Group of Eight summit in France last month he declared that the aim was to ensure that the Libyan people will be “finally free of 40 years of tyranny.” Is the United States obligated to participate in Libya’s reconstruction?

The Founding Fathers gave Congress the power to declare war for good reason: It forces the president to present his case in detail to the American public, allows for a robust debate to examine that case and helps build broad political support to commit American blood and treasure overseas. Little of that has happened here.

The nonbinding House resolution called on the president to issue a report to Congress answering 20 important questions about Libya. If the administration is wise enough to provide these answers promptly, that would be an example of the consultation that has so far been lacking.

Waging war is the most serious business our nation does. Obtaining congressional approval for war is not simple. But because getting out of wars is so difficult, the Founders did not intend that getting into them should be easy. The president should take the lesson from the House vote, retract his endorsement of the Senate resolution and propose a joint resolution with the force of law. Such steps would signal his willingness finally to engage Congress on the Libyan war and be the starting point for a real debate in both houses.

**The writer is a Republican senator from Indiana.