Yesterday President Obama announced his intent to establish a system of preventive detention for the "toughest" case of stopping would-be terrorists from "carrying out an act of war" even when they "cannot be prosecuted for past crimes, in some cases because evidence may be tainted." The one of the seniormost officials in the Justice Department’s Office of Legal Counsel, though, has expressed reservations to such a system in the past.

Before Marty Lederman became deputy assistant attorney general for the OLC, he was a prolific blogger and Bush-administration critic (and before that, an OLC attorney during the late Clinton and early Bush years). Here, for instance, is an Opinio Juris colloquy with Brookings’ Benjamin Wittes about various detention issues. Wittes argued that Congress should "treat these detentions openly and candidly for what they are: preventive incarcerations designed to keep extremely dangerous individuals from acting on their deeply held murderous beliefs and instincts," calling preventive detentions "a psychological Rubicon we simply need to cross."

Lederman objected:

Sorry, but I’m staying on this (constitutional) side of that line. “Dangerousness,” as such — particularly dangerousness as evidenced primarily by one’s “deeply held beliefs” — is not a constitutionally valid ground, standing alone, to indefinitely incarcerate persons without the protections of a criminal trial. Indeed, even if the dangerousness is demonstrated by past criminal conduct, that is not a permissible ground for noncriminal detention. “General deterrence” of dangerous persons, the Court has repeatedly held, is a function “properly . . . of criminal law, not civil commitment.” (Kansas v. Crane.)

Now, this isn’t a direct contradiction of Obama’s approach to preventive detention, since he hasn’t announced — or, apparently, even decided — what that approach is. And reading through Lederman’s post, he’s arguing that Wittes’ position is overbroad when considering restrictions that various judges have placed on the basis for detention. But the argument he presents is certainly in tension with the general idea of preventive detention, since all preventive detention is predicated on the idea of unprosecutable "dangerousness," which Lederman rejects as a "constitutionally valid ground" for "noncriminal detention."

We don’t yet know how Obama will define the category for eligibility into his preventive detention system. Could American citizens fall into that category? We don’t know. Obama gave as examples of possible preventive-detention targets "people who’ve received extensive explosives training at al Qaeda training camps, or commanded Taliban troops in battle, or expressed their allegiance to Osama bin Laden, or otherwise made it clear that they want to kill Americans." One of Daphne’s posts earlier this week quoted an Obama Justice Department filing further specifying the category –

"persons that the President determines planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001″; “persons who harbored those responsible for those attacks; “and “persons who were part of, or substantially supported, Taliban or al Qaida forces or associated forces that are engaged in hostilities against the United States or its coalition partners, including any person who has committed a belligerent act, or has directly supported hostilities, in aid of such enemy armed forces.”

–but a federal judge rejected that as overbroad as well. Accordingly, it’s unclear how federal judges will find any grounds for indefinite preventive detention to be constitutional. Lederman’s post, written long before he went into the administration, provides, at least, a legal foundation to ask whether it’s worth trying to test judges’ patience in the first place.

Crossposted to The Streak.