"Without congressional consent, the Obama Administration developed two legal arguments that could justify action against Assad. The first is simply that it is “in the national interest,” a vague test that Obama’s lawyers first used to justify the constitutionality of the Libya intervention in 2011. As it turned out, Obama did not strike Assad in 2013 and instead negotiated, with the blessing of the United Nations, an agreement that Assad would give up his chemical weapons. When the Security Council adopted the resolution outlining the agreement, it “agreed that in the event of non-compliance, it would impose ‘Chapter VII’ measures,” the U.N.’s term for the use of force.
Trump might argue that the missile strikes on Thursday night were simply enforcing the U.N. deal that Obama negotiated. However, the relevant U.N. resolution made it clear that the Security Council had to authorize the use of force before military action could be taken. Instead, Trump seems to have resorted to Obama’s “national interest” argument. In carefully worded remarks made at Mar-a-Lago after the strikes became public, Trump said, “It is in the vital national-security interest of the United States to prevent and deter the spread and use of deadly chemical weapons.” He made references to an international treaty, signed by Syria, against the use of chemical weapons, as well as the 2013 U.N. resolution. He also made a second national-interest argument: “the region continues to destabilize, threatening the United States and its allies.”
Harold Koh, who served as a legal adviser of the U.S. Department of State for the first few years of the Obama Administration and is now the Sterling Professor of International Law at Yale Law School, has articulated the legal justification behind the kind of limited military strike that Trump initiated.
“What I argue is that international law is supposed to protect human rights, not just sovereignty,” he told me. Koh argues that the Trump strike falls short of triggering the War Powers Resolution, which would require the President to seek congressional authority. “It’s not war. We haven’t gone to war against Syria,” Koh said. “We did a strike. And doing a strike is something that Congress has acceded to the President in cases where he claims a vital national interest.”
This interpretation rests on whether there are additional military actions, which the Administration has suggested there won’t be. “If this is a one-and-done, Congress isn’t going to challenge it,” Koh said. So far, he’s correct, as several congressional leaders, including prominent Democrats, have supported the action, and demanded a role for Congress only if Trump wants to go further. “Tonight’s strike in Syria appears to be a proportional response to the regime’s use of chemical weapons,” Nancy Pelosi said in a statement. “If the President intends to escalate the U.S. military’s involvement in Syria, he must come to Congress for an Authorization for Use of Military Force, which is tailored to meet the threat and prevent another open-ended war in the Middle East.” (Marco Rubio, too, has come out in favor of the strikes.)
Several legal scholars believe that the “national security” test is so vague that it makes almost any action constitutional. Jack Goldsmith, a former Justice Department lawyer in the George W. Bush Administration, argues in an essay at the Lawfare Blog that the two American interests cited by Trump—upholding a treaty and preventing the destabilization of a region—“will always be present when the President is considering military intervention,” and, thus, “ these interests provide no practical limitation on presidential power.”
In one of the many ironies of this episode, Trump is clearly coming down on the side of the humanitarian interventionists, like Koh, who have spent decades pushing for broad authority to use military force to protect populations that are threatened by their own governments.
“I’m not saying anything Trump does going forward isn’t awful,” Koh told me. “He’s obviously incompetent. But just to say that because I don’t like Trump—which I don’t—it’s illegal, is wrong. If you care so much about Syrian children, why doesn’t he let them in?” he said, referring to Trump’s travel ban on Syrian citizens. “It’s ridiculous. But that doesn’t make what he did just now illegal. That’s my point. Even a blind pig finds an acorn.”
Was Trump’s Strike on Syria Legal? - The New Yorker