Classical liberals and libertarians view war as a terrible engine of destruction, oppression, and government growth, holding with James Madison that “Of all the enemies to public liberty, war is, perhaps, the most to be dreaded, because it comprises and develops the germ of every other.” But libertarianism does not imply pacifism. Most libertarians have recognized that war, although evil, is at times a necessary evil. For the libertarian, then, the issue of war powers presents two questions: When is going to war justified? Who should have the authority to decide?

The first question is harder to answer than the second. Although libertarianism proscribes the initiation of force, it approves of self‐​defense. Because the legitimate state is an organization for collective self‐​defense, made necessary in part by the existence of other, aggressive states, few libertarians have been willing to rule out war in all cases.

But the issue of collective self‐​defense is morally more complicated than individual self‐​defense. As the historian Jeffrey Rogers Hummel has pointed out, when a state commits itself to armed conflict, it is actually declaring war on three fronts: against the other state, against the people of the other state, and against its own dissenting citizens who do not want to contribute to the war effort. Seeking to minimize the rights violations inherent in such an enterprise, libertarians have generally looked to the tradition of the “just war” to determine when war is legitimate. That ethical tradition, developed over the centuries by figures such as Cicero, St. Thomas Aquinas, and Hugo Grotius, holds that a nation may make war only when it is undertaken in a just cause, with right intention, as a last resort, and with a reasonable chance of success. Further, the means used must be proportional to the ends sought. According to the criteria set down by the notion of the just war, self‐​defense is the only indisputably legitimate justification for the use of force.

Of course, there is plenty of room for debate over what constitutes self‐​defense. Some libertarians hold that a country must wait until it is attacked before responding militarily. For others, preemptive war—attacking an enemy that is about to attack you—is permissible. A few libertarians have gone even further, arguing that preventive war can occasionally be justified—that in order to protect its citizens, a country can attack an avowed enemy before it grows strong enough to present a serious threat. But the farther one goes along the scale toward preventive attacks, the more speculative the threat, and the less clear it is that the war is truly a defensive one.

What branch of government should be empowered to resolve these issues and decide when war is necessary? In the British constitutional tradition, the decision at one time belonged to the monarch. Thus, in Commentaries on the Laws of England, Blackstone noted that,

the king has also the sole prerogative of making war and peace. For it is held by all the writers on the law of nature and nations, that the right of making war, which by nature subsisted in every individual, is given up by all private persons that enter into society, and is vested in the sovereign power: and this right is given up not only by individuals, but even by the intire body of people, that are under the dominion of a sovereign.

Libertarians reject this allocation of powers, holding that a decision as momentous as declaring war cannot safely be left to one man. Hence, they follow the American constitutional tradition. Wary of the executive’s propensity to wage war, the Constitution’s framers explicitly rejected the British model and granted the power to declare war to Congress. James Madison’s notes of the constitutional convention in 1789 report that only one delegate, South Carolina’s Pierce Butler, spoke in favor of granting the executive the authority to initiate war. His proposal was not warmly received. “Mr. [Elbridge] Gerry [of Massachusetts said he] never expected to hear in a republic a motion to empower the Executive alone to declare war.” For his part, George Mason of Virginia “was aghast at giving the power of war to the Executive, because [he could] not … be trusted with it.… He was for clogging rather than facilitating war.”

Accordingly, the Constitution specifies that the president lacks the authority to initiate military action. Article I, section 8 gives Congress the power “to declare War.” In the Framers’ view, in the absence of a congressional declaration of war, the president’s war powers would be restricted to being purely reactive. If the territory of the United States or American forces were attacked, the president was empowered to respond. Except for his power to “repel sudden attacks,” in Madison’s phrase, the president could not act without congressional authorization. As delegate James Wilson explained,

This system will not hurry us into war; it is calculated to guard against it. It will not be in the power of a single man, or a single body of men, to involve us in such distress; for the important power in declaring war is vested in the legislature at large.

For the first century and a half of our history, this constitutional allocation of war powers held. Large‐​scale wars—even nondefensive ones, such as the Mexican‐​American War of 1846—were declared by Congress; smaller wars were generally preceded by statutory authorization. But by the latter half of the 20th century, presidential wars small and large became a disturbingly common feature of the American political landscape. From President Harry Truman’s 300,000 troop “police action” in Korea to President William Jefferson Clinton’s 1999 air war over Kosovo, the decision to make war has increasingly been a unilateral one made by the president.

In fact, today the principle that the decision to initiate force belongs to the legislature is arguably healthier in Europe than in America. When NATO launched air strikes on Serbia in 1999, President Clinton refused to go to Congress for approval. However, other NATO countries made the decision to go to war legislatively: the Italian parliament had to authorize the strikes, and the German Bundestag had to be called into session to approve the participation of German forces.

In the United States throughout the 20th century, congressional control over the war power eroded, not simply as a result of executive aggrandizement, but also in part due to congressional complicity. The imperial presidency continues to grow largely because many legislators wish to avoid their responsibility to decide questions of war and peace. By delegating that responsibility to the president, they reserve their right to criticize him should military action go badly. For example, the use‐​of‐​force resolution passed by Congress immediately after 9/11 contains a sweeping delegation of authority to the president, authorizing him to make war on ‘‘those nations, organizations, or persons he determines planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001, or harbored such organizations or persons’’ [italics added]. In plain unambiguous language, the resolution leaves in the hands of the president the decision regarding when the evidence that a target nation has cooperated with al‐​Qaeda justifies war. Such broad delegations of legislative authority are constitutionally suspect in the domestic arena; surely they are no less so when it comes to questions of war and peace. As Madison put it: “Those who are to conduct a war cannot in the nature of things, be proper or safe judges, whether a war ought to be commenced, continued, or concluded.”

The war on terror presents special challenges for those who wish to restore the war power to Congress. Congress’s eagerness to shirk its deliberative responsibility, combined with a growing executive predilection for preventive war, will make it far more difficult to correct the constitutional balance of power, but ever more vital if we are to avoid unnecessary wars.

Further Readings

Fisher, Louis. Presidential War Power. Lawrence: University Press of Kansas, 1995.

Walzer, Michael. Just and Unjust Wars: A Moral Argument with Historical Illustrations. New York: Basic Books, 1977.

Wormuth, Francis D., and Edwin B. Firmage. To Chain the Dog of War. Dallas, TX: Southern Methodist University Press, 1986.

Gene Healy
Originally published