The United States has just launched a missile attack against Syrian air bases, apparently in response to the Assad regime’s use of chemical weapons against Syrian civilians. (The attack apparently was launched in the middle of President Trump's dinner with Chinese President Xi, and is not likely to make the Chinese very happy.) What legal authority for the use of force will President Trump assert under domestic and international law?
As a matter of domestic law, President Trump presumably relied on his Article II powers as Commander-in-Chief. The White House will likely file a report consistent with the War Powers Resolution tonight or tomorrow explaining the authority the President is asserting. Congress has not enacted an Authorization to Use Military Force against Syria. President Trump presumably decided that he did not want to ask Congress for authorization, in order to preserve the element of surprise and to avoid a delay or possible rebuff. His approach contrasts with President Obama, who as a candidate said that “The President does not have power under the Constitution to unilaterally authorize a military attack in a situation that does not involve stopping an actual or imminent threat to the nation.” When President Obama asked Congress to authorize the use of military force against Syria after Assad used chemical weapons in 2013, Congress failed to act.