President Donald Trump's decision to launch military strikes on Iran has triggered predictable partisan reactions in Washington. Yet the more consequential questions lie beyond the day-to-day political theatre: whether the strikes violate both the U.S. Constitution and international law—and what their regional consequences may be.
The constitutional issue is straightforward. Article I of the U.S. Constitution grants Congress the power to declare war. Article II designates the president as commander-in-chief. The division was deliberate. The framers sought to prevent unilateral wars by requiring legislative authorization for sustained hostilities.
After the Vietnam War, Congress attempted to reinforce that balance through the War Powers Resolution of 1973. The law requires presidents to notify Congress when introducing U.S. forces into hostilities and limits the duration of military action without congressional authorization.
Yet successive administrations have stretched or bypassed those constraints. Trump’s strikes on Iran now force the question once again: can a president launch a potentially major war without congressional approval?
Members of Congress from both parties have already questioned the legality of the operation. Sen. Tim Kaine (D-VA) introduced a War Powers Resolution requiring the administration to seek congressional authorization for further military action against Iran, but the measure ultimately failed to advance in the Senate. In the House, lawmakers also rejected a similar proposal by a vote of 212–219 that would have blocked additional military action without congressional approval. Sen. Chris Van Hollen (D-MD) warned that the U.S. risks entering what he described as an “illegal, regime-change war against Iran", reflecting growing concern among lawmakers that the administration may have bypassed Congress’ constitutional authority to decide when the nation goes to war.
This is not simply partisan rhetoric. It reflects a genuine constitutional dispute over who decides when America goes to war. But the constitutional question is only half the story. The international law implications may prove even more consequential.
Under Article 2(4) of the United Nations Charter, states are prohibited from using force against the territorial integrity or political independence of another state. This prohibition is the cornerstone of the post-World War II legal order.
There are only two recognized exceptions. The first is authorization by the U.N. Security Council. The second is self-defence under Article 51, which allows force only “if an armed attack occurs.”
International law sets a high bar for invoking self-defence. The International Court of Justice has repeatedly held—in cases such as Nicaragua v. United States and Oil Platforms—that self-defence requires both necessity and proportionality.
The traditional Caroline standard is even stricter: the necessity of self-defence must be “instant, overwhelming, leaving no choice of means and no moment for deliberation.”
Preventive war—striking to eliminate a potential future capability—has never been firmly accepted as lawful under international law. Nor has regime change ever been recognized as a legitimate objective of self-defence.
If the strikes on Iran were intended to degrade long-term military capabilities or encourage the collapse of the Iranian government, the legal justification becomes deeply questionable.
Some legal scholars have noted that even if certain Iranian leaders could be considered lawful military targets under the law of armed conflict, that does not resolve the more fundamental question of whether the use of force itself violates the U.N. Charter.
In other words, the legality of specific strikes does not automatically make the war lawful.
The context surrounding the strikes complicates matters further.
Reports suggest diplomatic channels had not been exhausted. Oman had been mediating indirect discussions between Iran and the U.S. related to Iran’s nuclear program. The Omani foreign minister described those talks as “intense and constructive,” suggesting negotiations remained active. If diplomatic pathways were still open, the legal requirement of necessity becomes harder to sustain. International law treats force not as a policy option but as a last resort.
Yet the military campaign appears to extend beyond limited deterrence.
According to analysts cited in recent discussions in Foreign Affairs, the joint U.S.–Israeli operation has targeted senior Iranian leadership and infrastructure in ways that suggest ambitions beyond immediate military objectives.
Indeed, some officials openly stated a goal of regime change. That objective carries profound risks.
History offers cautionary lessons about externally engineered political transformations in the Middle East. From Iraq to Libya, regime-change interventions have often produced prolonged instability rather than the orderly transitions their architects promised.
Even analysts sympathetic to pressure on Tehran warn that removing Iran’s leadership would not necessarily lead to a stable political outcome favorable to the U.S. The Iranian state retains deeply entrenched institutions and security forces capable of surviving leadership losses.
The regional implications could be even more volatile.
Iran sits at the crossroads of several geopolitical fault lines. Internal destabilization risks reverberating across neighboring states, particularly through Kurdish regions spanning Iran, Iraq, Syria and Türkiye.
Countries such as the United Arab Emirates have invested heavily in presenting themselves as stable financial hubs insulated from regional turmoil. But prolonged conflict involving Iran could undermine that carefully cultivated image.
Even influential figures within the Gulf appear uneasy. “This is Netanyahu’s war,” former Saudi intelligence chief Prince Turki al-Faisal recently remarked, arguing that Israeli Prime Minister Binyamin Netanyahu had convinced President Trump to support his views on Iran.
That perception matters. If regional actors conclude that the conflict primarily reflects Israeli strategic objectives rather than a broad international consensus, diplomatic tensions could deepen.
At stake is more than a single military campaign.
The prohibition on the use of force in international law exists precisely to prevent cascading regional wars. It is not merely a moral principle; it is a practical safeguard against spiraling retaliation and widening conflict.
None of this is meant to excuse the conduct of the Iranian government. Tehran’s domestic repression and its involvement in regional proxy conflicts have long contributed to tensions across the Middle East. But international law is not a reward for good behavior. Its purpose is precisely to restrain the use of force—even against governments whose policies are deeply objectionable.
For decades, the United States has portrayed itself as a defender of a rules-based international order.
That claim carries legal obligations.
If constitutional war powers can be sidestepped at home and the U.N. Charter’s limits can be stretched abroad, the consequences extend far beyond Iran.
They risk eroding the very norms that Washington has long insisted others must follow.
The constitutional test in Washington and the legal test under international law now converge on a single question: does law still meaningfully constrain power? For many observers—especially after the devastation in Gaza—the credibility of the so-called rules-based order already appears badly damaged. But that only raises the stakes. If legal limits collapse entirely, the risk is not merely hypocrisy but the normalization of unchecked war. If the answer is yes, then Congress must assert its constitutional role and demand clear legal justification for the use of force. The administration must articulate a case that withstands scrutiny not only in Washington but also in the broader international community.
If the answer is no, the Iran strikes may mark more than another Middle East crisis. They may signal the continuing erosion of the legal order that was meant to prevent wars like this in the first place.
History suggests that when power escapes the constraints of law, instability—not security—is usually the result.
Courtesy: Washington Report on Middle East Affairs
Faisal Kutty, J.D., LL.M. is a lawyer, law professor and regular contributor to The Toronto Star and Newsweek. He is affiliate faculty at the Rutgers University Center for Security, Race and Rights and Associate Professor of Law Emeritus at Valparaiso University. You can follow him on X @faisalkutty.