Read more of Slate's coverage of the Libya conflict.
Several days into a campaign of air and sea strikes against Libya, I agree with many of the arguments from critics of the intervention: President Obama acted imprudently in committing American forces to a conflict with an ill-defined national security justification. It is unclear how, on balance, a third war in a Muslim country helps our foreign policy goals. It is uncertain that the intervention will produce a regime more to our liking than Qaddafi's. It is hard to justify military action in Libya while the United States does not use military force in the face of brutal crackdowns by allies elsewhere in the Middle East. And it was especially unwise not to explain this action to the American people in advance or to better consult with and seek formal authorization, or at least political support, from Congress.
But that said, I depart from the critics of the Libya action, and from Sens. Obama and Hillary Clinton themselves circa 2007, and from the academic writings of Legal Adviser to the State Department Harold Koh on this one point: I do not believe that the military action in Libya is unconstitutional.
Legal scholars disagree about the original meaning of the Constitution's conferral on Congress of the power "to declare war." Many contend it required Congress to formally approve all uses of U.S. military force abroad, save, as James Madison said at the Convention, in situations needed to "repel sudden attack." Others maintain the "declare war" clause provides more leeway, allowing the president to use force abroad as long as the force does not rise to the level of "war," whatever that means. Yet others argue that the framers meant simply to give Congress the authority to signal under international law a state of war; the real work in controlling presidential initiation of force, under this view, was Congress' control over appropriations and the size of the standing army. There are many more theories about the original understanding. Even if we could definitively resolve this debate, which we can't, it is unclear why original intent—which in practice rarely determines contemporary constitutional meaning—should control outcomes in the context of presidential war powers, a context that as much as any is marked by radically changed circumstances.
Compounding the problem of indeterminate constitutional language is the fact that the courts have never resolved the question about the scope of the president's power to use military force abroad without congressional authorization. Almost all litigation seeking to resolve whether a war was properly launched has been dismissed as a "political question" or because the plaintiff lacked standing. As a result, the constitutional issue has been worked out almost exclusively by practice between the political branches and not by the courts.
That practice confirms that the president, under his commander-in-chief and other executive powers, has very broad discretion to use U.S. military force in the absence of congressional authorization. Presidents have done this, in military actions large and small, over 100 times, since the beginning of the republic. The largest and most consequential unauthorized military action is the Korean War launched by President Truman in 1950. Another big conflict without congressional authorization—and, indeed, in the face of an overt congressional vote that declined to provide such authorization—was President Clinton's Kosovo intervention in 1999. Some less significant unilateral uses of military force in the past 30 years include Haiti (2004), Bosnia (1995), Haiti (1994), Somalia (1992), Panama (1989), Libya (1986), Lebanon (1982), and Iran (1980). The executive branch has issued public legal opinions explaining the constitutional basis for most of these actions. (Some are listed here.)
Critics will claim that a pattern of consistently violating the Constitution cannot remedy the illegality of these actions. But that is not the right way to view this pattern. An important principle of constitutional law—especially when the allocation of power between the branches is at issue—is that constitutional meaning gets liquidated by constitutional practice. As Chief Justice William H. Rehnquist explained in his opinion in Dames & Moore v. Regan: "[A] systematic, unbroken, executive practice, long pursued to the knowledge of the Congress and never before questioned … may be treated as a gloss on 'Executive Power' vested in the President by § 1 of Art. II. Past practice does not, by itself, create power, but long-continued practice, known to and acquiesced in by Congress, would raise a presumption that the [action] had been [taken] in pursuance of its consent."