WASHINGTON — U.S. President Donald Trump’s missile strikes against Syria this spring didn’t need congressional approval because they fell below the threshold of “war in the constitutional sense,” the Justice Department said in a new memo Friday.

The strikes were on three Syrian targets in response to an alleged chemical weapons attack on civilians in a Damascus suburb. The justification for the strikes as warranted drew immediate criticism from several lawmakers. The Department of Justice said the strikes addressed vital national interests, though none were tied to self-defense.

Virginia Democrat Sen. Tim Kaine, a member of the Senate’s Foreign Relations and Armed Services committees, called the legal opinion “nonsense” and “ludicrous.”

“Is there any doubt that America would view a foreign nation firing missiles at targets on American soil as an act of war?” Kaine said in a statement. “The ludicrous claim that this President can magically assert ‘national interest’ and redefine war to exclude missile attacks and thereby bypass Congress should alarm us all.”

Before U.S., France and Britain launched 105 cruise missiles on April 14, the DOJ told the White House the strike would be legal. Trump, in April 2017, had also ordered targeted strikes on the Syrian government without seeking approval from Congress.

On Friday, the DOJ released the Office of Legal Counsel’s 22-page opinion on the latest airstrike, dated Thursday, and citing precedents under multiple administrations stretching back decades. These included President Barack Obama’s airstrikes in Libya and in Houthi-controlled territory in Yemen.

The memo, by Assistant Attorney General Steven Engel, asserted Trump’s justifications — promoting regional stability, stemming a humanitarian catastrophe and deterring chemical weapons use — were sufficient to bypass Congress.

Because the military action was limited in its nature, scope and duration — without ground troops or airplanes and directed only at the Syrian government’s chemical weapons — “it was not the kind of ‘prolonged and substantial military engagement’ that would amount to a war,” Engel’s memo stated.

On Thursday, House Permanent Select Committee on Intelligence ranking member Adam Schiff, D-Calif., and Kaine repeated calls for Congress to assert its war powers. Both have called for legislation to update the post-9/11 war authorizations, but the path is unclear.

“The Administration’s assertion of its power to order the use of force in the absence of Congressional authorization is broad enough to include almost any military action short of all-out war,” Schiff said in a statement. “This sweeping claim of power is an invitation to endless and unrestricted conflict, and begs for a congressional response.”