It’s to be expected that privacy will suffer a bear market after a terrorist attack or attempt. I’ve seen worse, of course, but was concerned this week to read a piece by Richard Epstein on the Hoover Institution web site that I think sounds needless anti-privacy notes. Professor Epstein is not only an important public intellectual, but a Cato adjunct scholar of which we’re proud, and a friendly professional colleague (to whose defense I’ll leap when he’s wronged).

The issue is what policies governments might adopt toward the end of terrorism prevention. Professor Epstein finds the statement of Massachusetts state senator Robert Hedlund (R‑Weymouth) to be a bridge too far. Hedlund says:

It’s not surprising that you have law enforcement agencies rushing out to use [the Boston bombing and subsequent manhunt] as pretext to secure additional powers but I think we have to maintain perspective and realize that civil liberties and the protections we’re granted under the Constitution and our rights to privacy, to a degree, are nonnegotiable…

You don’t want to let a couple of young punks beat us and allow our civil liberties to be completely eroded. I don’t fall into the trap that, because of the hysteria, we need to kiss our civil liberties away.

Professor Epstein calls that “dead wrong,” saying, “the last thing needed in these difficult circumstances is a squeamishness about aggressive government action.” Given the importance of preventing terrorism, claims of right against increased surveillance and racial or other profiling should be “stoutly resisted,” he says.

I agree with Professor Epstein that flat claims about a “right to privacy” shouldn’t limit surveillance. “Concern” with racial or ethnic profiling is not a sound basis for desisting from the practice. But I don’t take Hedlund’s statement to be a product of squeamishness, and I think it is in the main correct.

Where I think Professor Epstein goes wrong insofar as he wants law enforcement to have its way is in setting aside “technical difficulties” and “means-ends” questions as peripheral. For me, the Fourth Amendment’s bar on unreasonable searches and seizures demands coordination between means and ends in light of the technological situation (both in terms of doing harm and discovering it). It is not a given that government action is reasonable, and no amount of priority given to a threat makes an incoherent response reasonable and constitutional.

An illustration ad absurdum may help: Say the United States is credibly threatened with the possibility that a North Korean agent has snuck a nuclear weapon into the country. In response, the government institutes a program of 100% crotch checks at street corners in major cities. There is essentially no relationship between checking crotches and finding a nuclear weapon (which at its smallest is something like the size of a steamer trunk) or evidence of its whereabouts. It is unreasonable, even given the huge threat, to look for a North Korean nuke where it can’t be found. Searching the crotches of innocents is unreasonable. Affecting the persons of individuals as it does, due to the Fourth Amendment, it is unconstitutional.

The issues in terrorism prevention and punishment are closer, obviously, but it is at least worth discussing whether greater surveillance–greater-than-Boston-Marathon surveillance–would deter terrorists or make them easier to apprehend. Many terrorists are not concerned with worldly justice, and we have in the recent example two brothers who walked right through one of Boston’s most watched and filmed events to deposit their bombs on the street. The possibility of apprehension seems not to have deterred them.

The question raised by the Boston bombing seems not to be whether there should be surveillance, but rather whether the government should supplant civil society’s image-collection–dozens of private actors collecting data for pleasure and (all of our) security–with its own, watchful government net.

One can imagine a network of government cameras so dense, with special surveillance drones scrambled for any large event, that every visage is captured a number of times. If the vagaries of light and angle can be overcome, perhaps the dragnet includes facial recognition software and target tracking that passably identifies the whereabouts of everyone at all times they are in public.

I think it takes not just millions, but billions of dollars to deploy this surveillance architecture everywhere a terrorist act might occur. And for all this spending and cost in obscurity lost to law-abiding people, apprehension of suspects might improve by a few hours.

Such a program fails cost-benefit analysis. It is bad policy on the merits—unreasonable, in a word. And to the extent it is a search of things protected by the Fourth Amendment (not a given, though I’ve been toying with privacy in public since August 2001), it is unconstitutional.

The latest attack makes no case for racial or ethnic profiling. It has added literal Caucasians to the list of ethnicities involved in U.S. terror attacks, according to public consciousness. What profile algorithm turns up two Kazakhs and an American as abettors after-the-fact? Of course, terrorists come in all hues, including some of the most pale.

Most recent terror attacks in the United States have come from people claiming Islam as their religion. This fact is as undeniable as it is unhelpful in discovering terrorists. Knowing the correlation narrows the search for (our current, most concerning) terrorists down to one-fifth of the world’s population.

Profiling based on ethnicity or religion is a rather obvious statistical error that wastes the time and resources of law enforcement while it invades the interests, and sometimes rights, of the law-abiding. Even without considering equal protection or the right to practice one’s religion, the unreasoned nature of racial or religious profiling makes it a candidate for unconstitutionality if it results in a constitutional search or seizure. Claims of religious motivation can complete the picture, of course, when they inform an otherwise well-founded investigation and prosecution.

The right to have means and ends matched up in at least a plausible way is a right under the Fourth Amendment when it affects Americans’ security from government in their persons, houses, papers, and effects. That’s just a different expression of the right against unreasonable searches and seizures. This right is nonnegotiable, I think, and it is not a product of timidity about addressing terrorism. The government should not act incoherently in reaction to threats against the public, and I don’t think Professor Epstein would want it to.