On August 18, President Donald Trump said no talks with Iran were underway or scheduled, while the US naval blockade remained in force and Tehran insisted the Strait of Hormuz would stay closed until Washington met the terms of the June interim agreement. The impasse sharpens the most consequential question surrounding Trump’s legacy: not whether he wins or loses this war, but whether he leaves behind expanded presidential power, weakened constitutional checks on war making, and a diminished commitment to a rules-based international order. A president can leave office. A war can outlive him.

That is increasingly the danger confronting the United States. Trump’s confrontation with Iran has evolved from a military campaign into a constitutional and institutional test: Can an American president initiate and sustain major hostilities without explicit congressional authorization, and can Congress still meaningfully restrain him once the fighting has begun? The answer will shape far more than the remainder of Trump’s presidency. It will establish a precedent for every administration that follows.

The central issue is therefore not simply Trump’s foreign policy. It is the emergence of unchecked presidential power in the conduct of war. The United States entered the Iran conflict without a specific congressional authorization. Since then, the administration has advanced expansive interpretations of executive authority while Congress has struggled to reassert its constitutional prerogatives. The War Powers Resolution remains an important, if imperfect, mechanism for limiting the executive branch’s ability to sustain hostilities without congressional consent.

The danger becomes particularly acute when an administration can redefine the status of a conflict without ending the underlying military posture. The War Powers framework was designed to prevent presidents from converting temporary military action into an open-ended commitment: Absent congressional authorization, the law generally requires the president to terminate the use of US armed forces after 60 days. Yet the Trump administration has challenged the idea that this statutory clock should operate as an automatic constraint on presidential authority.

If lawmakers fail to reassert their authority, Trump’s most consequential legacy may be the normalization of a presidency capable of committing the United States to war without meaningful congressional authorization and leaving later administrations to deal with the consequences.

That creates a dangerous precedent. If a president can initiate hostilities, characterize them as limited or defensive, reinterpret the statutory clock, and then continue military operations without explicit authorization, the constitutional allocation of war powers becomes increasingly theoretical. The consequences are no longer hypothetical.

Congress has repeatedly attempted to invoke its war powers over Iran. In June, the House passed a measure directing the president to remove US forces from hostilities with Iran, and the Senate later adopted it. In July, the House again approved a war-powers resolution by 214-208, while the Senate rejected its own measure, 47-49. These votes expose the political problem: Congress is being asked to choose between institutional loyalty to the presidency and constitutional loyalty to the republic. For Republican lawmakers, the choice is especially consequential. Allowing a Republican president to expand executive authority without meaningful resistance establishes powers that a future Democratic president—or another Republican—could inherit in very different circumstances.

The question, therefore, is not whether Congress likes Trump. It is whether Congress is willing to allow presidential power to become self-expanding. Trump’s legacy also extends beyond the domestic constitutional order. His approach has placed pressure on the foundations of the liberal international........

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