On the evening of June 21, President Donald Trump announced via social media that the U.S. had bombed three sites linked to the Iranian nuclear program. In an address from the White House later that night, Trump called the U.S. mission a “spectacular military success.” In its attack the U.S. joined Israel, which has battered Iran with a series of airstrikes starting on June 12.
At the time, the Trump administration was in negotiations with Iran about a new version of the 2015 joint agreement limiting Iran’s nuclear ambitions, an accord from which Trump withdrew the U.S. in 2018. Trump said he had told Israel not to disrupt those talks. Israel went ahead anyway – Prime Minister Benjamin Netanyahu had disliked the 2015 agreement and in the long wake of the October 2023 Hamas attacks saw the chance to push the Trump administration in a different direction. Now, after some initial mixed signals, Trump has embraced this new conflict.
Back in January 2020 I wrote a piece after the U.S. assassination of Iranian general Qasem Soleimani that seems worth revisiting in light of the new U.S. attacks on Iran itself: “Does Trump need Congress’s approval to go to war with Iran?”
The short answer then was “yes.” The answer now is still “yes.” But the executive branch has built legal frameworks giving itself permission to take almost any military action the president sees fit. Thus getting to yes will require Congress to stop cheerleading for its own irrelevance.
The War Powers Resolution
As this site’s “Good to Know” piece on U.S. war powers discusses, the Constitution distributes war powers to both the president (as commander in chief of the armed forces) and Congress (through its authority to declare, regulate, and fund wars). To limit presidents’ ability to deploy military forces unilaterally, Congress enacted the 1973 War Powers Resolution (WPR), overriding President Richard Nixon’s veto.
According to the WPR, “the introduction of United States Armed Forces into hostilities, or into situations where imminent involvement in hostilities is clearly indicated by the circumstances” requires congressional authorization. That authorization could be a declaration of war or, more commonly in recent years, a specific statutory provision. For instance, Congress passed the 2001 Authorization for the Use of Military Force (AUMF) to respond to the 9/11 terrorist attacks. While that was aimed most directly at al-Qaeda and the Taliban, over time executive branch lawyers have used it to stretch far beyond those foes – to attack the Islamic State, say, which did not even exist in 2001.
Invoking the AUMF for Iran is a stretch
But Iran is a stretch far too far for the 9/11 AUMF. Brian Egan and Tess Bridgeman at Just Security argued in 2020 that, “we do not believe that there is any existing congressional authorization to use force against Iran,” and no such authorization has been passed since.
The WPR does allow the president to use force unilaterally (for a while) in “a national emergency created by attack upon the United States, its territories or possessions, or its armed forces” – contemplating that the president might, as discussed at the 1787 Constitutional Convention, need to “repel sudden attacks.” Certainly presidents using force without congressional authorization have often invoked self-defense.
But Iran had not attacked the United States – nor, at least in this context, Israel. Israel claimed it struck “preemptively” against an existential threat caused by Iran’s production of nuclear weapons; critics responded that Israel faced “no ongoing armed attack, incipient armed attack, imminent armed attack, or impending armed attack.” It does appear that U.S. intelligence estimates diverged from Israel’s. Indeed, in March 2025, Director of National Intelligence Tulsi Gabbard told Congress under oath that while Iran posed a potential threat to Israel and to U.S. forces in the region, the U.S. “continues to assess that Iran is not building a nuclear weapon and Supreme Leader Khamenei has not authorized the nuclear weapons program he suspended in 2003.” Sen. Chris Murphy (D-Conn.) claims the intelligence briefing he received “last week” also downplayed any imminent threat.
Trump responded bluntly to Gabbard: “I don’t care what she said,” adding, “she’s wrong.” Even if so it would still seem the “sudden attack” went in the other direction.
Presidential claims to unilateralism
In any case, presidents have built a latticework of legal justification they claim allows them to end-run both the WPR and that pesky requirement in the Constitution that Congress declare war.
The Justice Department’s Office of Legal Counsel (OLC), for instance, holds that Article II of the Constitution gives the president the power to use force when (1) the president believes there is an important “national interest” in doing so, and (2) when the force does not “rise to the level of a war in the constitutional sense.” War “in the constitutional sense” is the only kind that needs to be declared. Better yet, anything below that “level” does not even count as “hostilities” and thus avoids invoking the WPR as well.
So how to measure that level? According to the OLC, such a war is one requiring “prolonged and substantial military engagements, typically involving exposure of U.S. military personnel to significant risk over a substantial period.” President Barack Obama put it this way in 2011: The only “kinds of commitments” that would make the WPR relevant were those on the scale of the Vietnam War, “in which we had half-a-million soldiers there, tens of thousands of lives lost, hundreds of billions of dollars spent.”
This (re)definition allowed the Obama administration to claim that 2011 military operations in Libya did not activate the WPR. The Trump administration took the same route to justify its 2017 and 2018 airstrikes against Syria over its use of chemical weapons. Ongoing operations against Houthi rebels in Yemen (beyond immediate retaliation for attacks on U.S. ships that might qualify as self-defense) also took this legal route.
What happens next?
A lot depends on the answer to that question. Trump claims Iran’s nuclear sites were “completely and totally obliterated” and warned against any retaliation – in short, gambling this is a one-night, one-off attack, “limited and contained.” But that is hardly guaranteed. Indeed, the nature of the attack invites escalation that could lead to the “prolonged” engagement and “significant risk” OLC posits. In their 2020 analysis, Egan and Bridgeman write that the:
…factors the Executive traditionally considers … point toward the ‘war in the constitutional sense’ threshold being reached [in a conflict with Iran] … including but not limited to the use of force being directed at a large nation state, the exposure of U.S. forces in the region, and the potential that the use of force would not be limited or narrow but could … even point toward an intent to achieve regime change through force.
Of course, JD Vance claims that the U.S. is not at war with Iran, but “with Iran’s nuclear program.” It’s doubtful Iran itself will see the difference, especially since Trump had demanded Iran’s “UNCONDITIONAL SURRENDER!” even before the U.S. strikes and has since speculated on social media about the desirability of regime change.
Jack Goldsmith, a former OLC head, suggests that despite the lack of a direct attack the president may still be able to draw on past claims justifying action to bolster “collective” or “ancillary” self-defense. In an important 2023 piece he quoted Sen. Tim Kaine’s (D-Va.) summary of a Defense Department letter: DoD argued “that, by merely designating a group as a partner force, it can respond with military action to protect that partner force and its property if threatened by any group – even one that poses no direct threat to the United States, its Armed Forces or persons, nor is covered by an AUMF.”
Is the definition of “threatened by” elastic enough to overcome the absence of evidence of imminence? Goldsmith argued it could be – indeed that “just about any conceivable circumstance in which the president… would think it prudent to use force in the Middle East can be justified under an Article II self-defense theory.” He reinforced that conclusion in an insightful June 18 podcast with Obama White House Counsel Bob Bauer.
What does Congress say?
Even if that’s the case, it flows from the executive branch giving itself permission to act: That something “can be justified” or an argument is “legally available” does not prove the case. Indeed, OLC opinions tend to build up a patina of what looks like precedent by quoting and re-quoting past OLC opinions that have concluded the same thing – a habit of circular citation academics will recognize. The fact that the executive branch has decreed great discretion for the executive branch should not be taken as the final word on executive authority.
Under the Constitution, Congress has that final word. It was not obvious even to Alexander Hamilton or James Wilson, both strong supporters of presidential power among the framers of the Constitution, that the title of commander-in-chief of the armed services gave the president independent authority on when and how to use force. “This system will not hurry us into war,” said Wilson. In the 1950s, Congress debated whether the president had sole authority even to move troops from one place to another. In the 1970s, the WPR and other legislation marked Congress’s desire to push back against presidential overreach and take up its constitutional duties. During his 2024 presidential campaign, Robert F. Kennedy, Jr., now a Trump cabinet member, stated flatly that, “Except in cases of imminent danger to the nation, a president must be constrained in war-making through the check and balance of congressional authority.”
I suspect RFK won’t remind his new boss of that. But will Congress choose to use its authority? In 2020, a bipartisan coalition of legislators passed a bill terminating any military action against Iran without congressional approval, a bill Trump vetoed. Democrats (and a handful of Republicans) have already called for a similar legislative response now. But that seems unlikely, given Senate Majority Leader John Thune (R-SD) and House Speaker Mike Johnson’s (R-La.) sycophantic symphony to what Johnson called “the President’s decisive action.”
Indeed, as the OLC has noted with some satisfaction in its war powers opinions – and as scholars like Louis Fisher more angrily agree – Congress has frequently abdicated its authority, simply allowing presidents to act alone. Party loyalty tends to quiet dissent about presidential decision-making (and apparently only Republicans got advance briefings on the planned attack). A bonus for Congress is that if that action fails, prior deference allows legislators to complain about presidential action without taking responsibility.
Obviously how this plays out, globally and on Capitol Hill, depends in part on what the OLC has called the “fact-specific assessment” required to support unilateral force. The facts here center on not just on the time horizon of U.S. military engagement but on the plausibility of Israel’s claim of imminent threat and the Pentagon’s theories of “collective self-defense.” Public sentiment matters too, and in the days leading up to the attack only 16 – 25% of Americans expressed support for joining Israel’s attacks on Iran. Presumably that number will rise as Trump loyalists change their minds to match his decision – but how high?
Ultimately this comes to a matter of institutional – and Constitutional – duty. To paraphrase my conclusion in 2020: The wider consequences of the president’s decisions must be a matter for deliberation and accountability, key purposes for which Congress is built. In the end, good policy is as crucial as clear legality – is war with Iran a good idea?
That choice is not the president’s alone to make. In fact, if Vice President Vance is right that past policy failures in the Middle East can somehow be attributed to a long series of “dumb presidents,” engaged oversight of presidential decision-making is surely all the more important. James Madison, as usual, got there first, arguing for strong structural checks and balances in the new Constitution. “Enlightened statesmen,” he reminded us, “will not always be at the helm.”
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