Under Article I, Section 8 of the Constitution only Congress can declare war. Whatever that means, the fact is that Congress has not declared war since World War II. But the United States has certainly been involved in numerous armed conflicts since that time.
Because of lengthy indecisive conflicts in Korea and Vietnam, much of which were conducted outside the purview of Congress, the War Powers Resolution was passed by a veto proof two-thirds vote in 1973. It required the President to notify Congress within 48 hours of committing armed forces to an action and those troops may not remain in place for longer than 60 days unless Congress approves. This appears to contemplate a human physical invasion.
The War Powers Resolution allows the President to introduce troops into hostilities in three situations: when Congress declares war, or with specific statutory authorization, or when there is a national emergency created by an attack on the United States, its territories, or its armed forces.
(c)Presidential executive power as Commander-in-Chief; limitation
The constitutional powers of the President as Commander-in-Chief to introduce United States Armed Forces into hostilities, or into situations where imminent involvement in hostilities is clearly indicated by the circumstances, are exercised only pursuant to (1) a declaration of war, (2) specific statutory authorization, or (3) a national emergency created by attack upon the United States, its territories or possessions, or its armed forces.
Some commentators have rejected President Trump’s actions as falling within either the third emergency criteria for authorization since the U.S. has not itself been attacked, or the second authorization method which applies broadly to protecting against terrorist attacks, such as the 2001 Authorization to Use Military Force (AUMF) which was passed by Congress in response to the terrorist attacks of September 11th. This AUMF is quite broad and allows the President to use force against those who perpetrated the 9-11 attacks. This AUMF is currently cited as justification for use of force against a wide-ranging definition of terrorist groups.
In order to justify this action in Syria, the law must be read broadly, but more importantly, justification can easily rest on presidential actions taken by previous administrations. President Trump’s actions are nothing out of the ordinary. We only need go back to Obama’s actions in Libya where he maintained that he didn’t need authorization because U.S. involvement was limited and there was no “hostility” within the meaning of the War Powers Resolution. This interpretation was contrary to Department of Justice interpretations, but it has been used by previous administrations as well (Clinton’s bombing in the Balkans). Trump’s use of a singular target, not involving human troops, doesn’t even come close to matching the activity we undertook in the NATO operations against Libya. Presidents have been challenged in court by Congress, but none of these legal challenges have ever succeeded – courts frequently see them as nonjusticiable political questions.
Thus far President Trump has cited more general humanitarian reasons for taking this action. He has not indicated this will prompt more elaborate engagement in Syria. He is not indicating this is a war, and the action of sending only tomahawk missiles, and no boots on the ground, furthers the idea that this might even be outside the intent of the War Powers Resolution, which at the time of passage, was focused on the quagmire of Far East covert wars with high body counts.
In this case, waiting for an international solution seems useless. Assad’s illegal behavior has been ongoing for years and no one has seen fit to do anything about it. It would be unlikely the UN Security Council would approve of such an action anyway since any resolution would probably be voted down by Russia, Assad’s best friend right now.
So while the legal basis for Trump’s action may be weak, the broader view of deterrence and standing up for human rights is overwhelmingly strong in support of this action. Further, the public’s reaction seems to confirm this moral rectitude. Under Obama, the world had become less safe, but through thoughtful, strategic shows of force, Trump can bring much of the chaos back into balance. He may have been elected to save jobs, but he may be called upon to save the world.