So it is with U.S. counterterror activities. "The speaking of language is part of an activity, or a form of life," noted Wittgenstein. If the events of 9/11 constituted an "armed attack" and U.S. efforts to combat terrorism constitute "a war," then the international law of armed conflict applies; if 9/11 was a crime (albeit a horrific crime), then ordinary criminal law applies. And a great deal hinges on which legal framework we choose, for war rules are extremely permissive when it comes to the use of lethal force and other forms of state coercion, while the law enforcement framework is far less permissive.
In a war, the United States can lawfully kill enemy combatants with no judicial process whatsoever, and it can lawfully capture them and detain them indefinitely without trial. But if there's no war, suspects must be treated as innocent until proven guilty. They can't be killed just because officials believe they might commit further crimes in the future, and if they're apprehended, they need to be provided with lawyers and brought promptly before a duly established court.
The war/not-war distinction matters. If we can't figure out whether or not there's a war -- or where the war is located, or who's a combatant in that war and who's a civilian -- we have no way of deciding which rules to apply. But if we can't figure out what rules apply, we lose any principled basis for making the most vital decisions a democracy can make.
When can lethal force be used inside the borders of a foreign country? Which communications and activities can be monitored, and which should be free of government eavesdropping? What matters can the courts decide, and what matters should be beyond the scope of judicial review? When can a government have "secret laws," and when must government decisions and their basis be submitted to public scrutiny? Who can be imprisoned, for how long, and with what degree, if any, of due process? Who is a duck, and who is a rabbit?
Ultimately: Who lives, and who dies?
Forget about law -- and forget about lawyers
We can ask whether "snatch and grab" operations or drone strikes are "legal" until we're blue in the face, but in a world full of duck-rabbits, we won't learn anything interesting or useful.
Instead, we should focus on some very different questions: Do we prefer a world in which there are few constraints on the state's use of lethal force, which creates one set of dangers -- or do we want a world in which the state is more constrained, which creates a different set of dangers? How can we manage the dangers that accompany either vision? Or, if this is a false choice, what kind of world do we want to live in -- and how can we get there?
These are questions about morality, policy, and competing visions of the good, and I don't know how we will ultimately decide to answer them. But I do know one thing: Today, as in 2001, those who look to the law -- or to lawyers -- for guidance will look in vain.