Does Donald Trump have sole power to decide if and when to strike Iran? Or does Congress have a say?

As President Donald Trump decides whether the United States military should participate in direct military action against Iran, a bipartisan group of lawmakers is saying that Congress should have a voice in the decision.

U.S. military action against Iran has become plausible in recent days as Israel has pursued six days of attacks on Iran’s leadership, military assets and nuclear program.

But there are signs that the public is not fully supportive of a U.S. military strike against Iran. A Economist/YouGov poll conducted June 13 to 16 found 16% backing a U.S. military intervention, compared to 60% who opposed it. Among those who voted for Trump in 2024, the poll found 53% opposing a strike against Iran.

Noting such public concerns, some lawmakers from both parties have proposed legislation to require a say from Congress on whether to attack Iran.

In the House, Rep. Thomas Massie, R-Ky., has introduced a resolution cosponsored by several liberal Democrats. It says Congress "directs the president to terminate the use of United States Armed Forces from hostilities against the Islamic Republic of Iran … unless explicitly authorized by a declaration of war or specific authorization for use of military force against Iran."

Sen. Tim Kaine, D-Va., has introduced a similar resolution in the Senate.

"It is not in our national security interest to get into a war with Iran unless that war is absolutely necessary to defend the United States," Kaine said in a June 16 statement. "The American people have no interest in sending service members to fight another forever war in the Middle East. This resolution will ensure that if we decide to place our nation’s men and women in uniform into harm’s way, we will have a debate and vote on it in Congress."

Despite the cross-party constituency for slowing a U.S. attack on Iran, it’s unclear whether either chamber can muster a majority to pass such legislation.

If Congress doesn’t pass anything, it would continue a long-running divide between the president and Congress over who has the right to send U.S. troops into harm’s way.

How did the U.S. get to this point?

It has been a longtime aim of Israel to keep Iran from securing a workable nuclear weapon, since just a few of them could eradicate most of Israel’s population centers.

Since launching airstrikes June 13, Israel has set back Iran’s nuclear capabilities by damaging a uranium enrichment plant at Natanz and a site at Parchin where modeling was done for building nuclear weapons.

But analysts say that thoroughly curtailing Iran’s nuclear potential likely requires Israel to neutralize the heavily reinforced facilities at Fordo (sometimes spelled Fordow), where Iran’s most important uranium enrichment facility is buried deep under mountains about 125 miles south of Tehran.

To do that, analysts say, would require help from the U.S., which possesses the required military hardware Israel to significantly damage a well-protected site like Fordo. 

Whether to militarily join a direct Israeli offensive against Iran — which would be unprecedented despite the historically close ties between the U.S. and Israel — is now in Trump’s hands.

The presidency vs. Congress

But does the president have sole power to decide if and when to strike? Or does Congress have a say? The reality is that there are "overlapping authorities," said Joshua C. Huder, a senior fellow at Georgetown University’s Government Affairs Institute. 

Article I, Section 8 of the U.S. Constitution assigns the right to declare war to Congress. But the last time that happened was at the beginning of World War II, when Franklin Roosevelt was president.

Since then, presidents have generally initiated military activities using their constitutionally granted powers as commander in chief without having an official declaration of war in support of their actions.

Most controversially, in August 1964, President Lyndon B. Johnson asked Congress to back his effort to widen the U.S. role in Vietnam. He received it with enactment of the Tonkin Gulf Resolution, which passed both chambers of Congress, including the Senate with only two dissenting votes.

The U.S. Navy destroyer USS Maddox, one of the vessels involved in the Gulf of Tonkin incident, in the South China Sea in 1964. (U.S. Navy)

As the Vietnam War turned sour, lawmakers became increasingly frustrated at their secondary role in sending U.S. troops abroad. So in 1973, Congress passed the War Powers Resolution, which was enacted over a veto by President Richard Nixon. 

The resolution required that, in the absence of a declaration of war, the president must report to Congress within 48 hours of introducing armed forces into hostilities and must terminate the use of U.S. armed forces within 60 days unless Congress permits otherwise. If approval is not granted and the president deems it an emergency, then an additional 30 days are granted for ending operations.

Even under the act, there is understood to be some flexibility. "A single raid or even a series of raids would not require authorization," said Mark F. Cancian, a senior adviser at the Center for Strategic and International Studies, a national-security think tank.

Still, presidents have not been eager to cede their presidential prerogatives to Congress. Presidents typically frame any entreaties to Congress about military force as a voluntary bid to secure "support" for military action — action that’s often under way or planned imminently — rather than as "permission."

In recent decades, congressional consent has usually been accomplished by the passage of an "authorization for the use of military force" — a legislative vehicle that "has become the modern version of a declaration of war," Cancian said. 

Presidents who have received such authorizing legislation include Ronald Reagan (to oversee the handover of the Sinai Peninsula from Israel to Egypt, and separately to participate in a deployment to Lebanon that ended with a suicide attack that killed 241 American service members); George H.W. Bush (to oust Iraq’s Saddam Hussein from Kuwait); Bill Clinton (for military action in Somalia); and George W. Bush (to enter Afghanistan after the 9/11 attacks, and another to oust Hussein from power in what would become the Iraq War).

The post-9/11 authorization from 2001 is among the most controversial, because presidents of both parties have used its broad wording to support military action against a wide array of targets, using language that approves efforts "to prevent any future acts of international terrorism against the United States."

Almost a quarter century later, the 2001 authorization remains in force, despite being repealed by the Senate in a bipartisan 66-30 vote in 2023. (The House did not concur.)

What could be next?

During his second term as president, Trump has maintained strict discipline within his party. This suggests he would have the upper hand in a contest with Congress over war powers, experts said.

"Party loyalty is a powerful force on Capitol Hill, and Republican leaders in the House and Senate will be strongly incentivized to let the Trump White House use military force without congressional approval," said Matthew Green, a Catholic University political scientist.

However, the issue of going to war overseas is one that could test Trump’s degree of support within his own party. Some high-profile figures within Trump’s MAGA movement — including former adviser Steve Bannon and commentator Tucker Carlson — oppose an Iran attack and say they intend to hold Trump to his past rhetoric that he will keep the U.S. out of wars.

"If there is strong public opposition or a bipartisan desire for congressional authorization — if only to add legitimacy to the use of the American military — I could see Republicans persuading Trump to let Congress take action," Green said.

If Congress doesn’t act now, it could still get a second opportunity eventually, said Donald Wolfensberger, a former staff director of the House Rules Committee. Congress, he said, could "eventually flex its purse strings and call top brass on the carpet to ask, ‘Why was this necessary? Where’s it going, and for how long? And, at what cost?’"

Ultimately, congressional reaction "is determined largely by the majority party," said Lance Janda, a military historian at Cameron University. So with Republican control of both chambers until at least 2026, "I don’t see Congress getting involved" any time soon.

RELATED: Why a possible U.S. attack on Iran could break a longstanding U.S.-Israel pattern