The institution designed to prevent unilateral presidential action in matters of war and peace - the congressional declaration of hostilities, reinforced by the War Powers Resolution of 1973 - has lapsed into formalism without enforcement. It failed not because a president ignored it, but because no branch has exercised the authority to challenge the erosion of its substance. The question is not whether President Trump’s approach to Iran in 2026 was wise, but whether any institution remains capable of stopping a similar move if wisdom gives way to recklessness. The constitutional check exists on paper: the president may repel sudden attacks, but sustained military engagement requires legislative consent. Yet in recent years, that consent has been assumed rather than demanded, and the resolution’s sixty-day clock has been treated as a deadline for retreat - or, more commonly, a deadline for Congress to do nothing.

In England, the royal prerogative over foreign affairs was once absolute. The Civil War, the Glorious Revolution, and the gradual accumulation of precedent did not abolish the Crown’s power to declare war, but they shifted its exercise to ministers responsible to Parliament. When Pitt the Younger committed Britain to war with France in 1793, he did so with the understanding that Parliament would scrutinise the necessity, the means, and the cost. The check was not written in statute but embedded in practice: ministers answered questions, debates were held, budgets were contested. When the check was ignored - for instance, in the unauthorised incursion into Spain in 1808 by a minister acting without cabinet consensus - the backlash was not merely political but constitutional. The principle was reaffirmed not by decree but by repetition: the practice became the norm, and the norm became the expectation.

The American system, by contrast, attempted to codify the check in text. The Constitution gives Congress the power to declare war, raise armies, and appropriate funds; the president commands the armed forces. Yet in practice, Congress has ceded ground on all three fronts - not through repeal, but through abdication. It has not revoked the 1973 War Powers Resolution, but it has never invoked its mechanisms to force a presidential withdrawal. A vote to authorise force in 2002, later interpreted as covering actions far beyond its stated purpose, became a precedent for future delegation rather than a boundary. The institutional design is sound, but the practice has hollowed it out. The check remains, like a lock that no one has turned in years.

What is under pressure here is not simply the separation of powers, but the functionality of the check. There is a difference between a check that exists and one that is exercised. In the French Third Republic, the assembly held the power to vote war credits; yet after 1940, the lesson was not that the assembly should retain that power, but that it must be coupled with oversight, not just consent. The Fourth and Fifth Republics adjusted the balance, but always retained parliamentary authorisation for overseas deployments beyond a brief duration. The American system lacks that cultural reinforcement. The expectation is not that Congress will deliberate, but that it will eventually acquiesce.

The comparative method reveals a pattern: where legislative consent is treated as a formality, the executive’s freedom of action expands until a crisis forces a reckoning. In Turkey, the presidency has consolidated foreign policy authority under the 2017 constitution, and the assembly has not contested it - not because it lacks the power, but because it lacks the will. In Germany, the Bundestag’s consent is required for troop deployments, and it has exercised that power: it refused participation in NATO’s 2003 Iraq invasion and later constrained drone operations in Syria. The check worked because it was used.

Here, the absence of a contested vote on Iran is not neutrality - it is silence as complicity. The institutional design assumes that Congress will defend its prerogative, but decades of delegation have made that assumption fragile. The spirit of the American constitutional order - the expectation that power must be contested, not merely divided - has weakened. The danger is not that a president will openly flout the Constitution, but that no one will notice when the Constitution has already been reinterpreted by inaction.

The structural diagnosis is this: the separation of powers remains intact in form, but the check on war-making has become formal rather than functional. The principle at stake is not executive efficiency, but the preservation of liberty through institutional resistance. A well-designed constitution does not prevent all errors - it prevents irreversible errors. When Congress fails to assert its authority, it surrenders not just power, but the capacity to correct a mistake before it becomes history. The next crisis may not be Iran. It may be something precipitated by a president who has learned that silence is consent, and consent, once given, is permanent.