"I request a copy of this memo be given to Congress for immediate review," Kaine wrote in a letter to Secretary of State Rex Tillerson dated February 9. "If portions of the memo are classified, a SCIF can be made available."
SCIF, or Sensitive Compartmented Information Facility, refers to a secure room where authorized officials can read classified material without receiving copies.
The White House ordered the attacks in retaliation for a reported chemical weapons attack by the Syrian military against anti-government rebels.
According to Kaine’s letter, Trump authorized the strike citing the president’s constitutional responsibility as commander-in-chief to defend US national interests.
However, Congress has yet to see the actual memo spelling out details of the decision, Kaine noted in his letter.
"The fact that there is a lengthy memo with a more detailed legal justification that has not been shared with Congress, or the American public, is unacceptable," Kaine wrote.
Kaine cited concerns that the memo may also explain the Trump administration’s justification for this week’s airstrike against Syrian pro-government forces, which the White House claims was to intended to protect US-backed rebels from an attack by pro-government forces. Russia described the attack as an aggression against a sovereign state.