Editor’s Note: Today, Yoo and Ackerman discuss the presidential practice of unilaterally going to war. Previously, they debated the hypocrisy of the left and the right on the issue of war powers, the ongoing use-of-force resolution and the war powers language of the constitution. Later this week, they'll debate the possibility that there may be more important issues here than constitutional language.

Visiting Fellow John Yoo

Your argument that the original understanding of the Constitution gives Congress the sole authority on war would require a radical restructuring of the way we defend our country. My view would not require us to change the Constitution, find dozens of American wars unconstitutional, or overturn the consistent practice of presidents and congresses.

Neither presidents nor Congress have ever acted under the belief that military conflict requires a declaration of war. The United States has not declared war since 1941. It has waged numerous conflicts since, including Korea, Vietnam, Nicaragua, Panama, the Balkans, and Iraq.

You create a conflict between the Constitution and the judgment of dozens of presidents and congresses that these American wars were legal. If you are right, we must immediately delete Congress' power to declare war from the Constitution. Or we must overthrow a durable system that gives presidents the initiative, and allows Congress to control war through funding and its control over the size and shape of the military. Or we must ask the courts to stop wars that have received no declaration or authorization.

The Constitution's original understanding does not demand that we run any of these risks. While you correctly quoted Federalist 69 on Tuesday, you should note that Hamilton says only that as commander-in-chief the President does not have the power to declare war or to raise troops. When those words were written a declaration was not needed to begin a war--indeed, in the 100 years before the Constitution, the British only once declared war at the start of a conflict. Declarations define the legal status of hostilities under international law. They don't give Congress the sole key to launch the missiles.

Our Constitution usually makes clear when it requires a specific process before the government can act, especially when the executive and legislative branches share a power. It sets out detailed procedures for the passage of laws, the appointment of Supreme Court Justices, and the making of treaties. There are none for war. Our Constitution even declares that states shall not "engage" in war "without the consent of Congress"--exactly the limits you want on the President. Why didn't the Framers use this same language for the President if they wanted the same result?

A radical change in the system for making war might appease critics of presidential power. But it could also seriously threaten American national security. In order to forestall another 9/11 attack, or to take advantage of a window of opportunity to strike terrorists or rogue nations, the executive branch needs flexibility. It is not hard to think of situations where congressional consent cannot be obtained in time to act. Time for congressional deliberation, which may not even lead to smarter decisions, will come at the price of speed and secrecy.

The Constitution creates a presidency that can respond forcefully to prevent serious threats to our national security. Presidents can take the initiative and Congress can use its funding power to check him. Instead of demanding a legalistic process to begin war, the framers left war to politics. As we confront the new challenges of terrorism, rogue nations and WMD proliferation, now is not the time to introduce sweeping, untested changes in the way we make war.

John Yoo is a visiting fellow at AEI.