The president proceeded without congressional approval, citing national security concerns – a move not without precedent, but complicated nonetheless

Donald Trump’s decision to launch US military strikes in Syria without congressional approval has raised questions about the legality of the administration’s actions.



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The president’s retaliatory strikes against the Assad regime over its use of chemical weapons earlier this week was largely met with bipartisan support in Washington. But US lawmakers and legal experts were split over whether the strikes authorized by Trump were constitutional.

However, mostly everyone agreed: it’s complicated.

What does US law state?

The War Powers Resolution of 1973 was designed to serve as a check on the president, requiring the commander-in-chief to consult Congress when dispatching US combat troops into an armed conflict. But it enables the president to act unilaterally in the event of “a national emergency created by attack upon the United States, its territories or possessions, or its armed forces”, which has been broadly interpreted by recent administrations while approaching international crises.

The Trump administration has been quick to point to its notification of congressional leaders in both parties, as well as certain members on the relevant committees, ahead of the president’s action on Thursday. The White House has also framed the legality of the strikes as a matter of national security and protecting against the potential threat to US forces in the region.

In 2011, the Obama administration argued its bombing campaign in Libya was within the president’s legal authority as its intent was aimed at “preserving regional stability and supporting the [United Nation Security Council’s] credibility and effectiveness”.

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So what role does Congress play?

Under the US constitution, the president cannot declare war absent congressional approval. But recent administrations, through the use of drone strikes and so-called special operators (as opposed to ground troops), have created a decidedly lax interpretation of military involvement.

When Barack Obama was seeking to respond to Bashar al-Assad’s use of chemical weapons in 2013, he asked Congress to authorize the use of military force through what is known as an AUMF (authorization for use of military force). But the president notably underscored that he did not require congressional approval to take limited military action, contending instead he deemed it the appropriate thing to do.

Congress did not ultimately hold a vote on a new AUMF, with many Republicans in particular taking a stance against doing so under Obama. Some argued the president had the authority to act unilaterally, seemingly not wanting to incur the political risk that has accompanied military conflict since Congress voted in favor of George W Bush’s invasion of Iraq in 2003.

How does Trump’s action differ from Obama’s?

Although Obama did not proceed with military action against the Syrian regime, his administration eventually launched airstrikes in both Syria and Iraq targeted at Islamic State. For that action, lawyers in the Obama White House relied on the AUMF passed by Congress in 2001.

That AUMF provided George W Bush with the authority to exercise military action against countries, organizations and other groups involved in the September 11 attacks. Although the terrorist group in question at the time was al-Qaida, the measure has since been employed as the justification for broader military action in the Middle East as the US government has characterized Isis as an offshoot of al-Qaida.

While the Trump administration has carried forth Obama’s military campaign against Isis, the president’s authorization of 59 Tomahawk cruise missiles at a government airbase was the first US strike targeted at Assad’s regime in the six-year Syrian civil war. Though many acknowledge the 2001 AUMF has provided cover, even if questionably, to US military action in Syria, legal experts largely agree a direct attack on Assad’s military requires a new AUMF.

Trump, incidentally, advocated against Obama taking military action in 2013 and insisted on the president seeking authority from Congress:

Donald J. Trump (@realDonaldTrump) The President must get Congressional approval before attacking Syria-big mistake if he does not!

What are legal experts saying?

Mary Ellen O’Connell, a professor of international law at the University of Notre Dame, said the legality of Trump’s action “depends on which body of law is in question”.

“There’s no doubt that international law, the UN charter, prohibits the use of military force for retaliation or for reprisal, punishment,” she said. “You can only use military force in self-defense, and he did not.”

While the president should seek authorization from both the US Senate and House of Representatives under domestic law, O’Connell acknowledged “a longstanding conflict between presidents and Congress” with respect to what military action necessitates a new AUMF.

She also took issue with the Trump administration’s suggestion that the chemical weapons attack posed a national security threat to the US, stating: “Nobody thinks Assad could use chemical weapons on Americans.”

Matthew Waxman, a law professor at Columbia University and former national security official in the George W Bush administration, also said that the causal relationship between Assad’s strikes, Trump’s retaliatory strikes, and threats to American forces “is a pretty stretched one”.

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“But all recent presidents have taken a broad view of the president’s constitutional powers to launch military strikes to protect American security interests,” he said.

Basing the legality on humanitarian interests was also tricky under the US law, Waxman said, as “the constitutional precedents for defending American security interests are much stronger than the precedents for purely humanitarian action”.

Hina Shamsi, the director of the National Security Project at the American Civil Liberties Union, was far less equivocal.

“The use of chemical weapons against civilians is horrific, but the fact is that President Trump’s military action violates the constitution and US treaty obligations under the UN charter,” she said.

“There’s no legitimate domestic or international law basis for it, and it’s telling that the administration hasn’t even tried to provide one.”

What are members of Congress saying?

Most US lawmakers were reluctant to criticize Trump’s initial response to Assad, with a majority of members of both parties declaring it important to establish that the use of chemical weapons would not be met without consequence.

But a handful of members of Congress were quick decry Trump’s action as unconstitutional.

The Virginia senator Tim Kaine, who swiftly dubbed the strikes “unlawful” following Thursday’s announcement, said the 2001 AUMF applied to use of force against a terrorist organization but not Assad.

“I encourage the White House to bring the legal rationale promptly before us,” said Kaine, who sits on the Senate foreign relations committee, “as well as a full strategy to indicate what our posture is going to be vis-a-vis Syria.”

“The constitution is clear that Congress needs to authorize war ... If missiles landed at Andrews air force base fired by another nation, is there any doubt that we would consider it an act of war? We would consider it an act of war.”

Republicans were far more inclined to back Trump’s authority, noting that the administration had not yet outlined any pending action that would require Congress to play a role.

“He has the authority as commander-in-chief to respond to emergencies and take action,” said the Florida senator Marco Rubio, who forcefully praised Trump’s missile strikes.

Rubio, who voted against Obama’s proposed airstrikes in 2013 as part of a vote on the Senate foreign relations committee, further noted the presence of US troops in Syria, whom he said Trump was obligated to protect.



“The presence of sarin gas and a regime willing to use it is a clear and immediate threat to those troops,” Rubio said, following a briefing with Gen Joe Dunford, chairman of the joint chiefs of staff.



Maryland senator Ben Cardin, the top Democrat on the Senate foreign relations committee, said the issue of legal authority had not been discussed during the briefing.



“There is a strong belief that the president has inherent powers as the commander-in-chief to act on similar missions similar to what we saw yesterday,” Cardin said.



The South Carolina senator Lindsey Graham, one of the more vocal hawks, said he believed Obama had erred by approaching Congress four years ago and was glad Trump did not follow suit.

“My advice to the president: just do it.”