Article I of the Constitution unequivocally gives Congress, not the president, the “power . . . to declare War.” The Founding Fathers sought to avoid a situation where one man had the power to commit the nation to war by himself. Even Alexander Hamilton — the biggest supporter of sweeping presidential power among the framers of the Constitution — recognized that “the Legislature have a right to make war” and that “it is . . . the duty of the Executive to preserve Peace till war is declared…”Some small-scale uses of force may not rise to the level of a war and therefore can be undertaken by the president alone under his authority as Commander in Chief of the armed forces. President Reagan’s 1986 airstrike on Libya might be an example, as were Bill Clinton’s 1998 missile strikes against al-Qaeda base camps….There is some ambiguity about exactly where a small-scale “conflict” ends and “war” begins. But the fact that we cannot draw a precise line between the two does not mean that there aren’t cases that clearly fall on one side or the other. We can’t draw a precise line between people who are “short,” those who are of “average” height, and those who are “tall.” But we can still easily recognize that Shaquille O’Neal is tall. Similarly, a large-scale military action against a foreign government clearly qualifies as “war.”
Although ISIS is a nonstate entity, that does not mean that large-scale military action against it cannot qualify as a war. The US campaign against al Qaeda is surely a war, as is Israel’s conflict with Hamas, even though neither is a formally recognized government. Indeed, there are obvious parallels between ISIS and Hamas, as both are terrorist organizations that control a substantial territory despite lack of international recognition as states. At this point, the territory controlled by ISIS is likely significantly larger than that controlled by Hamas in Gaza.
For the moment, administration officials say that the president has issued only a “narrow” authorization for airstrikes intended to protect US personnel on the ground in Irbil and Baghdad, and to rescue besieged civilian members of the Yazidi minority who may be massacred by ISIS.
It is possible that the military action envisioned will indeed be so small-scale that no congressional authorization is required. But what if it turns out that very limited strikes and stepped-up assistance for Kurdish and Iraqi government forces are not enough to impede ISIS’ advance? In that event, any significant increase in US military involvement would require congressional authorization. In addition to meeting constitutional requirements, congressional support could also give military intervention valuable political legitimacy and staying power. If the president goes in on his own, political support could evaporate quickly if anything goes wrong. Since he alone would bear the blame, congressional leaders – especially those from the opposition Republicans – would have every reason to hang him out to dry. For that reason, among others, it is generally better to enter a war only if there is a broad political consensus in favor of doing so, including both the president and Congress.