When President Barack Obama unilaterally ordered the bombing of Libya in 2011, I argued that Obama was acting "in violation of the U.S. Constitution and the War Powers Act until he gets Congress's approval." The exact same argument now applies to President Donald Trump's unilateral bombing attack on Iran.
Article I, Section 8, of the Constitution places the power "to declare War" exclusively in the hands of Congress. The president of the United States, whose own limited powers are separately enumerated in Article II, possesses no lawful authority to launch a war on his own.
Historical evidence from the framing era of the original Constitution supports the point. In a 1798 letter to Thomas Jefferson, for example, James Madison observed that "the constitution supposes, what the History of all [Governments] demonstrates, that the [executive] is the branch of power most interested in war, & most prone to it. It has accordingly with studied care, vested the question of war in the [Legislature]."
