With much of the world bracing for Donald Trump’s new missile strikes on Syria, the president’s legal authority to attack Bashar Assad is conspicuously AWOL.

Assad isn’t subject to either of the two authorizations Congress passed after 9/11 to bless the use of military force. He’s not part of al Qaeda, nor a successor organization like the Islamic State—which is dubiously covered under the 2001 authorization as it is—nor is he part of Saddam Hussein’s regime.

The closest Trump aides have come to providing a domestic legal justification for striking Assad, offered by his former secretary of state, is that Trump possesses the inherent authority to do so as commander-in-chief, a gigantic assertion last used—and ultimately abandoned—by George W. Bush’s administration.

The implications are large and ominous, according to a member of the Senate Armed Services Committee. “If [Trump] strikes Syria without our approval, what will stop him from bombing North Korea or Iran?” Sen. Tim Kaine (D-Va.) told The Daily Beast on Tuesday.

Trump’s casus belli is the apparent chemical weapons assault Assad launched on the Damascus suburb of Douma on Saturday. That assault, from which at least 70 are dead after an estimated 500 people were exposed, is “correctly characterized as a war crime,” said Mary Ellen O’Connell, an international law specialist at the University of Notre Dame. But that doesn’t mean the U.S. can legally respond, absent a United Nations Security Council resolution, which Assad’s ally Russia will veto.

“Military force against Syria will violate international law just as surely as the use of chemical weapons. President Trump wants to enforce the law by breaking it,” O’Connell said.

Much like last April, when Trump ordered 59 Tomahawk missiles to hit a Syrian airfield used to stage a chemical assault on Khan Sheikhoun, Trump is likely to shoot first and answer questions about his legal authorities later—if ever. His administration has yet to declassify a legal memorandum, penned by the Justice Department’s Office of Legal Counsel around the time of last year’s Syria strike, that court papers describe as “advice and recommendations to the president and/or other senior Executive Branch officials regarding the legal basis for potential military action.”

That memo is the subject of a Freedom of Information Act lawsuit from the Protect Democracy Project, a bipartisan group centering around Obama administration attorneys. On Monday, the group filed an emergency motion for its release, citing the “potentially imminent military action” in Syria flowing from its contents.

“ A statement of policy masquerading as a statement of law. ”

“[T]his recent development indicates that the withheld documents are serving as the working law that embodies the agencies’ law and policy governing legal authority for the use of military force,” the group contended in its Monday filing.

But the memo, for now, remains withheld. The closest its contents have come to a public discussion is a comment made by Rex Tillerson, the former secretary of state, in October.

Asked, months after the fact, why the April 2017 strike on the Shayrat airbase was legal, Tillerson told Kaine that Trump ordered the strike “pursuant to his power under Article II of the Constitution as Commander in Chief and Chief Executive to use this sort of military force overseas to defend important U.S. national interests.” Since the strike came as a reprisal to Assad’s Khan Sheikhoun chemical attack, Tillerson continued, it was “justified and legitimate as a measure to deter and prevent Syria’s illegal and unacceptable use of chemical weapons.”

That was a statement of policy masquerading as a statement of law. Assad’s most recent chemical massacre was devastating to Syrian civilians, but there is no state of war between the U.S. and Assad—neither asserted by the White House as flowing from a declared war, nor declared by Congress itself. Accepting Tillerson’s assertion would open the door further to an “unbounded” presidential power, said Allison Murphy, counsel for the Protect Democracy Project, all without so much as an explanation.

“In our democracy, the Commander-in-Chief’s power is constrained by the Constitution and Congress, and the rule of law,” Murphy said. “If we concede that President Trump has unilateral authority to decide to strike Assad, do we concede he has similar authority to unilaterally strike North Korea, or Iran, or France?”

Yet Congress typically does accept such broad assertions of presidential warmaking authority, as it’s the path of least political resistance. Congress stood idly by as Bill Clinton attacked Serbian forces in Kosovo in 1999 and as Barack Obama attacked Muammar Gaddafi in Libya in 2011. Both of those were lengthy military campaigns, not one-off strikes like Trump’s 2017 cruise-missile strike on Shayrat.

It’s unclear if Trump is looking to do another one-off or something more substantial, since Assad’s repeated chemical attacks over the past year demonstrate that Trump’s 2017 strike ultimately failed. But Trump is suggesting that he’s all but given the order.

He pledged on Monday to make “some major decisions over the next 24 to 48 hours.” By the evening, ahead of a meeting with senior military officers, Trump said his new national security adviser, John Bolton, had “picked the right day” to start work, as “you’re going to find it very exciting.”

On Tuesday, Trump canceled what would have been his first trip to South America, scheduled for late this week, “to oversee the American response to Syria,” explained spokeswoman Sarah Huckabee Sanders. If that wasn’t enough, Trump has every incentive to change the subject from the extraordinary search warrants served on his personal attorney.

Bolton is no fan of international law, having famously quipped that the United Nations secretariat building could lose ten of its 38 stories and it “wouldn't make a bit of difference.” O’Connell, of the University of Notre Dame, said that an attack on Syria absent U.N. approval to reinforce a norm against chemical weapons usage is “reminding me of the old U.S. strategy in Vietnam of destroying a village to save it. And we know how well that turned out.”

Representatives of the National Security Council did not respond to a request for comment. The Justice Department and State Department declined comment. A Pentagon representative, Eric Pahon, declined comment about the legal predicates for any forthcoming strikes, but said: “The president and his national security team are consulting closely with allies and partners to determine the appropriate response.”

“Assad must face consequences for the horrific atrocities he’s committed against the Syrian people,” Kaine told The Daily Beast. “But President Trump needs to finally lay out a Syria strategy and come to Congress for approval if he wants to initiate military action. He’s a president, not a king, and Congress needs to quit giving him a blank check to wage war against anyone, anywhere.”