Judge Richard Posner (of the U.S. Court of Appeals, and co-author, with U of Chicago Economics Professor Gary Becker, of one of the most informative blogs on the Internet) has been doing singularly important research on post-9/11 intelligence reform. (See these books, here and here). He has a very interesting op-ed in the WSJ this morning (and up on Opinion Journal), urging the creation of an American version of Britain’s famous domestic spying agency, MI-5.

Well taken are his criticisms of the FBI for its infuriating inability to enter the world of 21st Century information technology and for its law enforcement mentality. (The latter is not criticized per se, but rather for being ill-suited to the vastly different skills of intelligence collection and analysis). Still, proponents of an American MI-5 frequently fail to address two big considerations, and, unfortunately, Judge Posner does not address them today either:

1- In this political environment, where, as we saw last week, we can’t even data-mine – even with personal identifying information omitted – without stirring enormous controversy, how on earth could one ever convince congress to create a stand-alone domestic intelligence agency? That is, aren’t we better off, as a practical matter, trying to fix the FBI than to start from scratch?

2- Most people who provide useful information about those who pose threats to our nation do it under the threat of prosecution (or to win leniency for what would otherwise be mega-sentences). Obviously, upstanding members of the community tend not to know much of anything about the inner-workings of terrorist organizations — it’s the bad guys you must induce to cooperate. For all the admitted problems of marrying up competing skill-sets, the reason combining the law enforcement and intelligence functions makes sense is because you can seamlessly leverage prosecution to obtain intelligence. Wouldn’t we be losing a lot by dividing those functions? An MI-5 is going to want to horde its sources for pure intelligence purposes rather than turn them over to the FBI and DOJ for prosecution; but if you don’t threaten them with prosecution, you very likely will not get the most deeply held intelligence secrets.

Britain’s 7/7 bombings demonstrate that having a dedicated domestic intelligence agency is far from fool-proof. (Judge Posner, to his great credit, has been superb in explaining why intelligence is such a difficult challenge, and why we may never have a very high batting average when it comes to preventing attacks.) While his piece today is typically thought-provoking, I don’t think it makes the case that an American MI-5 is either possible or necessarily desirable.