I think everyone should head over to The New Republic to read the debate going on over wiretaps. Let's look at a sample bit of text:

Yet the mere fact that a suspected or even a known terrorist has a U.S. phone number in his possession would not create probable cause to believe the owner of that phone also a terrorist; probably most phone conversations of terrorists are not with other terrorists. The government can't get a FISA warrant just to find out whether someone is a terrorist, though that's what it most needs to know. Nor can it obtain a warrant to intercept communications between two persons both of whom are in the United States, even if they are suspected of being members of a terrorist sleeper cell. These are crippling limitations.

So a terrorist has an American phone number in his possession. But, for some reason, we're unable to tap the phone in the foreign country. (Let's say we just busted in his door and he's gone, leaving behind a single rolodex.) As Posner himself states, "most phone conversations of terrorists are not with other terrorists" so we're left with the unenviable position of tapping an American citizen's phone in the hope that the terrorist will call him.

Does Posner not see the ramifications of this? By this logic, since the American could be talking to a terrorist, we must tap his phone. Why stop there? Why not simply tap every American's phone line if they make calls to the middle-east? Since, clearly, the vast majority of the people tapped are innocent (which the FBI is none too happy to deal with), expanding the search would make little difference.

This, precisely, is the reason that FISA exists: if a single individual is thought to be acting with terrorists, a wiretap would be issued. If, instead, fifty to a hundred names show up in the magical terrorist rolodex, then there is no probable cause to assume that any one of those names is the name of a terrorist.

Is probable cause a "crippling limitation"? Do police in America frequently butt up against it? If police suspect someone of murdering another person, but have no probable cause, are they someone being morally evil by refusing to spy on the person?

Posner's argument goes against everything America stands for: the right to be considered innocent until proven guilty, the right to have the law proceed in an orderly fashion, and the right against unwarranted search and seizure.

Posner claims that these ideas are crippling limitations. But if we abandon them, the terrorists will have already won.