Under US law, Trump faces an impending deadline to end the Iran war. What happens if he ignores it?

US President Donald Trump is quickly approaching a deadline to wrap up his war against Iran – or he’ll be in breach of US law.

Under the 1973 War Powers Resolution, a US president can only launch a war without congressional approval for 60 days. After that, Congress either has to declare or authorise the war – or the president must end the operations.

Even though there is currently a ceasefire between the US and Iran, the resolution would still apply to the naval troops and ships responsible for maintaining the US blockade of Iranian ports.

So, what happens if the 60-day deadline passes and Trump refuses to pull out?

What is the War Powers Resolution?

The War Powers Resolution was passed by Congress over then-President Richard Nixon’s veto in November 1973. It was a major piece of legislation designed to curb presidential usurpation of the congressional power to declare war. It came just after the withdrawal of US troops from the Vietnam War, which had not been authorised by Congress.

The law hasn’t been very successful since its passage because of its loose legal language, the numerous exceptions and qualifications, and the large number of loopholes that presidents and their advisers have discovered.

Certainly, no president since Nixon has been significantly constrained by the law. Those who have initiated conflicts without congressional approval have paid little more than lip service to its provisions.

Congress has also contributed to the failure of the War Powers Resolution through its reluctance to defend its constitutional and statutory rights to declare war.

Notwithstanding its past ineffectiveness, it may be premature to write off the War Powers Resolution in the current conflict. The main reason: it provides a mechanism for wary Republican lawmakers to try to bring an end to an unpopular war.

What does the law say?

The statutory end-date for the war comes into effect by way of two sections of the War Powers Resolution.

Under section 4, the president is required to submit a report to Congress within 48 hours of introducing US troops into “hostilities” and explain the constitutional and legislative authority under which the action was taken, the justification for the action, and the estimated scope and duration of the US involvement.

This triggers a 60-day clock under section 5 of the law. If Congress has not declared or authorised the war by then – or extended the deadline – the president must end the military action.

The beauty of this provision, at least as far as members of Congress are concerned, is that it is automatic. Legislators don’t have to do anything to implement it. And because no vote is necessary, they don’t have to go on record opposing the president’s military and national security policy.

Trump submitted his report on the war with Iran on March 2, which means the 60-day deadline expires on May 1.

So far, Congress has not responded by declaring or authorising the war, though Republicans have blocked numerous Democratic legislative efforts to end the war or constrain Trump’s ability to act without congressional approval.

Congress also has the option of extending the 60-day limit for a maximum of 30 days. This would require a vote in both the House and Senate.

Republicans are growing uneasy

The major difference between this war against Iran and other wars of recent US presidents is that this one is going extremely badly for Trump.

A new poll by Reuters and Ipsos this week found that just 34% of Americans support the US conflict with Iran.

This time, there has been no “rally-around-the-flag” effect supporting Trump’s military incursion. Members of Congress, ultra-sensitive to their constituents’ opinion, are not running scared of opposing Trump on this issue, either. Many would be risking electoral backlash by going on the record in support of the war.

Republican Senator John Curtis of Utah, for example, has written an essay saying he will not support the war after the 60-day deadline passes without congressional approval. Other Republicans have echoed his sentiments.

Given his general contempt for the Constitution and statute law, Trump will probably disregard the legal mandate to withdraw US troops. He is more likely to claim that the War Powers Resolution is unconstitutional, as Nixon did when he vetoed it in 1973. As such, he may seek to challenge the law through the courts.

So, what happens if Trump does ignore the deadline? This depends on how members of Congress react. Democrats are reportedly exploring a lawsuit against the administration, though this has proven difficult to do in the past.

Trump could also claim the law doesn’t apply because US forces are not currently engaged in direct hostilities in Iran, as then-President Barack Obama did when the 60-day clock lapsed during the US military operations in Libya in 2011.

When Trump sent formal notification to Congress on March 2, he made a point of saying he was acting under his “constitutional authority as Commander in Chief and Chief Executive”, neither of which give him the power to commit the US to war without congressional approval.

He did not acknowledge the War Powers Resolution except to say that his report was “consistent with” it – a standard form of wording used by his predecessors who have all demonstrated some reluctance to adhere to its provisions.

In the past, when presidents and Congress have clashed over the War Powers Resolution, they have usually reached some accommodation, but it has depended on the circumstances and often favours the president.

This time it could be different. Trump is badly managing an unpopular war with wafer-thin majorities in Congress, six months out from the midterm election.

If US troops are still engaged in the Middle East on May 1, the War Powers Resolution could take on a relevance it hasn’t had for more than 50 years.