Virginia Sen. Tim Kaine and California Rep. Adam Schiff wrote a letter to President Donald Trump on Monday requesting the White House provide the legal basis for the attack on Syrian President Bashar al-Assad's regime
when Congress has the constitutional role of declaring war.
"It has now been over two weeks since you ordered the strike on the airfield, and your Administration has yet to put forward any detailed legal analysis or justification for that action under domestic and international law," the Democrats wrote.
"The legal justification for an attack on the Syrian government is not an afterthought, but rather a first order consideration, and something that is vital for the American people to understand at the outset," they added.
The Trump administration has asserted that the Syrian strike — where US warships hit a Syrian airbase with 57 Tomahawk missiles in response to a chemical weapons attack on Syrian civilians — was legal under the President's authority to defend US interests.
"I acted in the vital national security and foreign policy interests of the United States, pursuant to my constitutional authority to conduct foreign relations and as Commander in Chief and Chief Executive," Trump wrote in a notification letter to Congress required under the War Powers Act. "The United States will take additional action, as necessary and appropriate, to further its important national interests."
The new letter from Kaine and Schiff underscores the attention Democrats in Congress are calling to Trump's foreign policy and the use of military force, particularly as the administration talks tough against North Korea.
In their letter, the Democrats said the need to explain the legal justification for the use of force was "all the more necessary" as tensions rise on the Korean Peninsula.
"While the President has the authority to use force to defend our service members and allies from an imminent threat, a preemptive strike could easily spiral into a full-fledged war with a nuclear-armed adversary," they wrote.
Kaine and Schiff have been two of the most vocal Democrats pressing for Congress to pass a new war authorization, known as an Authorization for Use of Military Force. Their push began when the Obama administration began its military campaign against ISIS, and Trump's Syria strike has injected a renewed sense of urgency into the effort.
So far, however, Congress has not moved closer toward passing a war authorization for either ISIS or the Assad regime.
Kaine had long said that the ISIS campaign is not legal. Both this administration and the Obama administration before it have justified the military action on the basis of the 2001 war authorization passed after the September 11, 2001, terrorist attacks, but Kaine argues that it should not apply to the current campaign because ISIS did not yet exist.
Kaine also charged there was no legal authority for Trump to strike the Assad regime the morning after the attack.
CNN legal analyst and University of Texas national security law professor Steve Vladeck wrote that the legality of the strikes is complicated, because the Constitution gives Congress the power to declare war but declares the President as commander in chief.
Vladeck said that the Trump administration's next steps in Syria may ultimately determine whether the Trump administration will have to go to Congress for a formal war authorization to use military action in Syria.
"It will now likely be very difficult as both a practical and legal matter for Trump to use additional military force against the Assad regime without more specific approval from Congress," he wrote. "Until and unless that happens, though, there likely will be no formal resolution of the legal question -- and, thus, one more equivocal precedent in the separation of war powers."