The framers of the U.S. Constitution lived in an age of muskets and messengers, when war moved slowly and left time for Congress and the president to confer. But by giving Congress the power to declare war and the president command of the military, they set the stage for lasting struggle over U.S. forces.
President Trump's decision to launch airstrikes on Iran's nuclear facilities without first consulting Congress has drawn sharp criticism from lawmakers who say the move bypasses their constitutional authority to declare war.
Speaking Monday on NPR's Morning Edition, Sen. Mark Kelly, D-Ariz., said that while there's little Democrats can do to force the administration to seek congressional approval, the president should still respect constitutional norms. "The administration should comply with the Constitution," Kelly said. "Traditionally, presidents have done that. I know recently, sometimes with certain actions, when it is viewed as protecting the safety of our country, presidents can act, and then they should be able to notify us."
Sen. Tim Kaine, D-Va., was more direct in his criticism. Appearing Sunday on CBS' Face the Nation, he said: "The United States should not be in an offensive war against Iran without a vote of Congress. The Constitution is completely clear on it. And I am so disappointed that the president has acted so prematurely."
So what does the Constitution actually say?
Article I gives Congress the power "to declare War, grant Letters of Marque and Reprisal, and make Rules concerning Captures on Land and Water." Article II, meanwhile, designates the president as "Commander in Chief of the Army and Navy of the United States," giving the executive authority to direct the military once conflict has been authorized.
"I think it's pretty clear that the framers thought that any time we were going to be making the decision to go to war with another country, that was going to be a decision for Congress," says Rebecca Ingber, a law professor at Cardozo Law School in New York.
Yet presidents have long sent U.S. forces into combat without a formal declaration of war. As an early example of this, Stephen Griffin, a constitutional law professor at Tulane Law School, points to the Quasi War, a limited naval conflict between the fledgling U.S. and its erstwhile Revolutionary War ally, France. It took place at the end of the 18th century but there was never any formal declaration of war between the two countries.
That trend accelerated after World War II, driven by a combination of new military technologies and evolving global institutions.
"The creation of the atom bomb changed the game," says Griffin. In the early republic, communications were slow and military deployments took months. After 1945, however, "things were speeded up," Griffin notes. "You would need sometimes an instant response."
He also points to the influence of the United Nations, which the U.S. helped establish in 1945. The U.N. Charter prohibits the use of force by member states except in self-defense or with Security Council approval. Even in the U.S., that framework helped shift legal discussions away from formal declarations of war and toward concepts like "use of force," he says.
Critically, Griffin says, the Constitution doesn't require Congress to issue a formal declaration of war. What matters is legislative approval — such as an authorization for the use of military force (AUMF). "The constitutional requirement is about legislative approval," he explains, "not literally picking up a document that says, 'Declaration of War' and signing it."
While the Korean War did not have a formal declaration, the Gulf of Tonkin Resolution — widely regarded today as a misleading statement of the facts of a naval encounter between a U.S. destroyer and North Vietnamese gunboats — did draw the U.S. further into the Southeast Asian conflict. Passed it in 1964, that resolution authorized President Lyndon Johnson to take military action in Southeast Asia. President George H.W. Bush got an AUMF for the Persian Gulf War in 1991. During the 1999 Kosovo crisis, President Bill Clinton launched a NATO bombing campaign against what was then Yugoslavia without congressional authorization.
Debate over these conflicts frequently saw the legislative and executive branches at odds. In the wake of the Vietnam War, Congress sought to claw back some authority by passing the War Powers Resolution of 1973, which sought "... to fulfill the intent of the framers of the Constitution ... and insure that the collective judgment of both the Congress and the President will apply to the introduction of United States Armed Forces into hostilities." The resolution requires the president to notify Congress within 48 hours of deploying U.S. forces into hostilities and to end the deployment within 60 days unless Congress authorizes or extends it. It became law after Congress overrode President Nixon's veto.
Michael Glennon is a professor of constitutional and international law at the Fletcher School of Law and Diplomacy at Tufts University who was also a legal counsel in the late 1970s for the Senate Foreign Relations Committee, where he handled legal issues surrounding the War Powers Resolution.
"Vietnam became the turning point for Congress because their constituents were being killed," Glennon says.
Initially, he and others were optimistic that the War Powers Resolution would correct the imbalance between Congress and the president and prevent another Vietnam. Instead, the resolution has been largely ignored by presidents of both parties, he says. Over time, administrations have routinely sidestepped its requirements — informing rather than truly consulting Congress, and continuing military operations without proper authorization.
Glennon believes the Constitution "does prohibit the president from using armed force in attacking a country such as Iran unless there is an attack on the United States or the threat of an imminent attack."
That didn't happen, he says, "and I conclude, therefore, that this was unconstitutional," he says.
But Glennon acknowledges that "generally speaking," the requirement under the 1973 resolution to consult Congress has been complied with. "But in some circumstances, Congress has been informed [ahead of time] rather than consulted. That's not what the War Powers Resolution contemplated."
Ingber, of Cardozo Law School, agrees. "Even this administration … is at least nodding toward those requirements. Even Secretary of Defense [Pete] Hegseth said, [the administration is acting] 'in accordance with the War Powers Resolution.' "
That modicum of respect for at least part of the resolution underscores that it "is widely considered constitutionally justified under Congress' 'necessary and proper' power," Griffin says.
If the attack on Iran is truly a one-off — as the administration contends — the need to get authorization from Congress for the use of military force is likely unnecessary, he says.
But "if this turns into tit-for-tat with Iran, Trump should get an authorization. That would satisfy the War Powers Resolution — and strengthen his legal position," according to Griffin.
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