Writing in the New York Times, Michael Kinsley defends treating Umar Farouk Abdulmutallab (the al-Qaeda operative who recently tried to blow up an airliner over Detroit) as a criminal defendant rather than an enemy combatant. He argues that, since any line to be drawn between waging war and engaging the criminal-justice system is going to be arbitrary, the U.S. border is as good a line as any. That is, al-Qaeda terrorists captured abroad are enemy combatants while those captured at home are criminal defendants, entitled to all the rights provided by our Constitution and statutes.

The problem is that the lines between law enforcement and war are not arbitrary (but rather well defined by law and tradition) and that choosing the U.S. border as a nice, bright line is not driven by military strategy, logic, or law. There is nothing sacred about American territory. Indeed, at least two major wars — the Revolutionary War and Civil War — and numerous military conflicts with Indian tribes were prosecuted on American soil. This war can be (and has been) fought here as well as in Afghanistan, Iraq, or Yemen. In fact, the United States is the enemy’s favored battleground, because this is where al-Qaeda’s most desired targets — American civilians — are most heavily concentrated. This is why the victims of 9/11 died in New York, Washington, and the fields of Pennsylvania, rather than at American facilities and installations abroad.

Nor, in fact, is the line Mr. Kinsley proposes arbitrary; it is ideological. Adopting a war-abroad/law-enforcement-at-home rule is nothing but an exercise in political triangulation. It indulges the Left’s fundamental disdain for the use of military force, while permitting the Obama administration to claim that it actually is trying to protect the American people by taking the fight to the enemy. Read between the lines — or read the lines. Mr. Kinsley contrasts our roles “as a liberal democracy and as a legitimately aggrieved superpower.” Why is it, exactly, that those two things are inconsistent? We are, in fact, a legitimately aggrieved liberal democracy that happens, also, to be a superpower.

At bottom, law enforcement and war do not mix well because they begin with very different assumptions and, as a result, are governed by fundamentally different rule sets. It is those assumptions that the Obama administration and the Left in general find problematic. Thus, our civilian criminal-justice system is designed to constrain the overwhelming power of the state vis-à-vis an individual criminal defendant. Ask any criminal-defense lawyer: The prosecution has the edge at almost every point. It decides who to investigate and who to charge, has resources that (however constrained) far outweigh those of any ordinary defendant, and controls the evidence, crime scene, and witnesses.

Presented with these realities, our body polity has decided at least since the 1960s to temper and handicap the government’s ability to investigate, prosecute, and punish criminal misconduct. This is why, as Mr. Kinsley correctly describes, many a murderer, rapist, or child molester goes free. To be sure, despite all of these constraints on the police, prosecutors, and prison authorities, in the final analysis, the state is overwhelmingly powerful as compared with even the most deviant and potent criminals. This is true even in cases of organized crime and drug gangs. However well armed and ruthless such groups may be, any properly functioning state will be capable of marshalling sufficient force to maintain an overwhelming predominance.

In war, the challenge to governmental authority is not individual but collective, and is far more dangerous as a result. Foreign belligerents have broader means and a stronger motive to disrupt the social order than common criminals do. The power of their armaments and the pervasiveness of their ideology can often be traced to the direct or indirect support they receive from other international players. All states at some basic level have an interest in maintaining civil law and order — and however much foreign police or judicial systems may hamper U.S. law enforcement in certain cases, they do not actively seek to promote the criminal activity involved. By contrast, in war, foreign states may choose to support — directly or indirectly — enemy belligerents, effectively augmenting their reach and capabilities.

As a result, governmental power is necessarily augmented during wartime. This is especially the case in liberal-democratic states, where that power is ordinarily subject to greater limits than in authoritarian regimes. It is, of course, this very augmentation that the Bush administration’s critics found so unacceptable after Sept. 11, 2001. The alternative, however, is accepting greater risk to the civilians al-Qaeda wants to target. The right way to proceed, consistent with the law, morality, and history, is to treat captured enemy personnel as enemy combatants, subject to the laws of war. By contrast, criminals — including individuals who commit terrorist acts but, whatever their ideological predilections, are not members of entities such as al-Qaeda that have been engaged in an armed conflict with us (this would include Timothy McVeigh and Major Nidal Malik Hasan) — should be treated as criminal suspects subject to the workings of the criminal-justice system. Treating an al-Qaeda operative who enters the United States to carry out an attack as a common criminal not only denies the nature of this challenge we face, but it works to level the playing field to our disadvantage.