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Your Questions Answered: Can Congress Stop President Trump's Illegal War Against Iran?

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Amid President Donald Trump's unconstitutional war against Iran, Ƶexperts break down who has the power to declare war — and how Congress can assert its war powers.
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Christopher Anders,
Director of the Democracy and Technology Divison,
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March 5, 2026

In the early morning of February 28, President Donald Trump announced that the U.S. and Israel had started bombing Iran. He said that the lives of courageous American heroes may be lost and we may have casualties. That often happens in war. What he failed to mention was that he doesn't actually have the power to declare war; only Congress does.

Since then, at least six U.S. service members and over 1000 civilians in the region have been killed, and these deaths will only continue to increase as the war drags on. But war powers are not a matter of executive discretion. They are a matter of law, written right into Article I of the Constitution itself.

The Ƶdoes not take a position on the political decision of whether military force should be used against any specific country. But for more than 50 years, we have insisted that under the Constitution, the power to declare war belongs solely to Congress. It's a position we've consistently explained to presidents of both parties, from President George H.W. Bush to President Joe Biden, and now to President Trump.

Below, an Ƶexpert explains what war powers are, how presidents have used — and abused — them, and ways that Congress can end this unconstitutional war.

What does the Constitution say about war powers — and why?

Recognizing the world's long history of immense human and economic costs of war, the framers of the Constitution did not leave the decision to go to war to a single individual. Instead, the Constitution gives Congress the sole authority to declare war, except in truly exceptional circumstances of defense against an attack or imminent peril. There's been no credible indication that those extreme circumstances existed before President Trump attacked Iran. The Constitution also says that the president can direct military operations, but only after Congress has declared war or authorized the use of force. This separation of powers is intentional. The founders of America had seen European monarchs drag nations into war without accountability. They knew that concentrating all war-making power in one person would endanger our collective safety, liberty, and democracy. The Constitution gives this solemn power exclusively to Congress as the branch of government closest to the people.

Can the president unilaterally declare war?

No, only Congress can declare war or authorize the use of force. After the Constitution was drafted, some of its framers wrote the Federalist Papers to explain and defend the Constitution to the new nation. James Madison wrote in one of the papers that the president could act alone to order the military to repel a sudden attack on the United States, but only if the Congress did not have time to return to the capital and debate and vote on whether to declare war — and even then, Congress would debate and vote on the use of force when it could convene.

Then, in the wake of the Nixon administration's secret bombings of Cambodia during the Vietnam War, Congress enacted the War Powers Resolution, a law that sets a specific process for Congress to bring an end to any use of force that the president takes without the specific authorization by Congress.

That's why, this week Congress is invoking a provision of the War Powers Resolution that would require the president to end any unauthorized use of force in Iran if both the Senate and the House of Representatives say so. According to the War Powers Resolution, the unauthorized use of force must also end if 60 days pass after the use of force first started.

Can Congress Use its Funding Authority to Reassert Its War Powers?

Yes. If the unconstitutional war continues, Congress can use its power to deny funding and help end it. The Constitution provides that Congress alone appropriates funds for the military. Each year, Congress enacts legislation to fund each department of the government. Earlier this year, Congress passed an appropriations bill to fund the Department of Defense through September 30, 2026. The bill provided enough money for the Pentagon to carry out its regular operations, but it did not provide money to carry out a massive war against Iran. War is enormously expensive, as the military uses or loses munitions, equipment, aircraft, fuel, and other supplies. The government is quickly plowing through billions of dollars for a war that Congress never authorized, and Americans don't want.

The Trump administration has already realized that it is running out of money and will very soon ask Congress to pass a supplemental appropriations bill to fund the Iran war. This bill would likely provide billions of additional dollars for the military to spend, including for war expenses. And just like any other bill, both the House and the Senate will have to vote on it, before it's sent to the president to sign.

If the war against Iran continues, members of Congress need to listen to their constituents and say no when the Trump administration pleads for more money for its illegal war that Congress and the American people never wanted.

What do wars abroad mean for Americans at home?

The ACLU's long history of insisting on constitutional war powers limitations stems from the recognition that war powers must be exceptional, as the framers intended. When presidents evade Congress to start conflicts, they don't just violate the Constitution, they put people's lives and rights in danger.

Over the past 100 years, we've seen the government use the justification of war to:

  • Pass the Espionage Act during World War I. This made it a crime to obstruct military effort, which the Justice Department and the U.S. Postal Service interpreted very broadly to include almost any language that appeared to oppose the war, the draft, or both. This fundamentally unfair and unconstitutional law is still on the books.
  • Arrest people who opposed being drafted for war, including the ACLU's very own founder Roger Baldwin.
  • During World War II, forcibly transport and incarcerate more than 120,000 people of Japanese descent based on nothing more than their ethnicity.
  • Deploy the National Guard during a rally opposing the Vietnam War and the U.S.'s invasion of Cambodia, which resulted in the killing of four unarmed protestors.

More recently, we can look at the U.S. response to the tragic attacks on September 11, 2001. Instead of meeting violence with justice, transparency, accountability, and a commitment to fundamental rights, the U.S. government set up a domestic nationality-based registry for 10 years and tore apart Muslim families and communities. It tortured people and locked them up without charge or trial. It wrongly put Americans on watchlists and passed the Patriot Act, beginning an era of mass surveillance that persists today.

Instead of going down another dark path of what the Secretary of Defense admits is , it's past time for Congress to reassert its role as the people's representatives. We all must demand that no president gets to take the country to war without public debate and democratic accountability to the American people and their representatives in Congress. Tell Congress to

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