“…unauthorized by the Constitution, without sanction of Congress, to go beyond the line of defense.” President Thomas Jefferson, May, 1801 Letter to Congress on protection of American merchant ships against the Barbary pirates of Tripoli.

What are the President’s war powers? They are defined in the Constitution. “The President shall be the Commander in Chief of the Army and Navy of the United States,…” (Article II, Section 2). The President is in charge of the military, but no war powers are conferred directly on the President. Instead, the Constitution confers those powers on Congress, “The Congress shall have Power to declare war…” (Article I, Section 8).

What did the Founders mean when they assigned the war powers that way? The First Barbary War provides a clear picture of their intent.

No sooner had we gained our Independence and formed our Nation than the protection of Europe against the pirates of the Barbary Coast ended. We were on our own and the States of Morocco, Tunis, Algeria, and Tripoli knew it. For 15 years, all four States sanctioned pirates to capture our merchant ships and ransom our seamen or sell them into slavery.

Without a Navy capable of protecting our ships, the United States was forced into a treaty with the Sultan of each State. We paid up to $1 million to each as part of their protection racket. All but Tripoli observed their treaty. Tripoli accepted the tribute but continued their piracy.

Seeing the need for defense against France and the Barbary States, President John Adams built up the Navy and by 1798 Congress was able to authorize Adams to protect our merchant ships against French privateers.

Then, as one of its last acts before Jefferson took office as President, Congress passed a law authorizing six ships “officered and manned as the President of the United States may direct…in the event of a declaration of war by the Barbary powers to protect our commerce and chastise their insolence…”

Immediately upon Jefferson’s inauguration in 1801, the Pasha of Tripoli demanded the next year’s ransom. Jefferson refused and the Pasha declared war on us.

Jefferson sent a naval force only sufficient to defend our merchant vessels. As he expressed in that May letter to Congress, he did not have the power to take action against Tripoli itself, stating further, “…this important function [is] confided by the Constitution in the Legislature exclusively…”

While Congress did not vote a formal declaration of war, it did authorize Jefferson “to cause to be done all such other acts of precaution or hostility as the state of war will justify.” Thus empowered, Jefferson ordered the attack on Tripoli and we prevailed.

Even for a strict act of self-defense, Jefferson relied on Congress to provide legislative authorization. He knew as did Congress (and John Adams, who waited for Congressional authorization to send ships against French privateers) that a President cannot exceed even a “line of defense.”

Over the years, Presidents, both Democratic and Republican, have inched past the “line of defense” going so far as to wage war in all but name, yet we know what the Founders intended. As shown by Jefferson, the Founders knew how a President could use executive power to wage war in his own interests and, in the Constitution, they designed a clear safeguard against it.

Jefferson understood and obeyed the Constitutional limits to his war powers. But, if another President does not, it is up to Congress to enforce those limits. Not all Congresses have exercised this responsibility. Let’s hope that this one will.