“Congress has spoken,” Congressman Ro Khanna announced last week. “Trump cannot declare war with any nation, especially Iran, without coming to us first.”

President Trump has sent wildly uneven signals regarding Iran since he backed out of the nuclear deal with that country. At times, he has seemed to signal a determination to enter into conflict with Iran; at others times he has backed off. What is clear is that tensions remain. They have flared repeatedly in recent days, amid the wrangling over the shooting down of a mysterious drone over the Strait of Hormuz, reports of the seizure of a British-flagged oil tanker, and a claim by Iran that it is arresting CIA spies.

This is a confusing and conflicted moment, when irreversible errors could be made. If there is to be any assurance that the United States will not lurch into another war in a region where so many lives were lost after the 2003 invasion of Iraq—and where so much of the country’s international credibility has been sacrificed—Congress must be prepared to check and balance this administration. The president must know that he cannot start a war without the constitutionally mandated approval of the House and Senate.

The good news is that the House has put the president on notice. The chamber voted 251-170 on July 12 for a bipartisan measure, authored by Khanna (D-CA) and Congressman Matt Gaetz, (R-FL), that is intended to force the president to respect the constitutionally mandated authority of Congress to make decisions regarding war and peace. Specifically, the Khanna-Gaetz amendment to the annual National Defense Authorization Act prevents federal funds from being used for any military force in or against Iran without congressional authorization.

Crafted with an eye toward ending presidential power grabs, the amendment makes it clear that past authorizations for the use of military force—enacted after the September 11, 2001, terrorist attacks on the World Trade Center and the Pentagon, and before the 2003 invasion of Iraq—cannot be invoked by the president in order to justify the use of military force against Iran.

“This is a historic moment for Congress,” wrote Khanna. “Although President Trump campaigned on ending costly wars oversees [sic], his chosen advisors, one [of which was] the architect of the Iraq war, and actions to increase tensions with Iran prove he is far from living up to that promise. With more than 25 Republicans voting in favor of passage, this amendment is proof that opposition to war with Iran transcends partisan politics. Some of the President’s closest allies voted for this amendment. Americans came together around the idea that we must avoid a war with Iran.”

Khanna’s point is a critical one. The coalition that has supported a reassertion of congressional authority over questions of war and peace with Iran is broad. It is bipartisan. It extends from right to left. It includes conservative groups such Americans for Prosperity and Freedom Works, along with progressive groups such as Demand Progress. It includes groups that promote diplomatic resolutions to conflicts in the region, including J Street and NIAC Action. It includes veterans groups such as VoteVets and Concerned Veterans for America, as well as longtime advocates for peace and disarmament, including the Council for a Livable World, the Friends Committee on National Legislation, Peace Action, the Ploughshares Fund, and Win Without War.

There is little constituency for war with Iran outside the desperate circle of neoconservative hawks that has attached itself to the current administration. Yet there is a fear that war might occur. “The administration’s approach of maximum pressure against Iran has been a dismal failure and has escalated the risk of war, whether by design, accident, or miscalculation,” explains Diana Ohlbaum, the senior strategist and legislative director for foreign policy with the Friends Committee.

But there does not need to be a war. Congresswoman Barbara Lee (D-CA) is right when she says, “Trump’s Iran policy is responsible for this self-inflicted crisis.” And she is equally right when she says, “The Trump Administration has no authorization to go to war with Iran and must seek authorization from Congress.”